Have you considered consolidating all of the data onto the same spreadsheet and then using a pivottable to analyse your data. A pivot table can aggregate and rank your data with ease.
To consolidate your data all you could insert an new column which shows the spreadsheet origin.
We can still look for a formula solution of course but a pivot table could solve a problem like the one you have shown in that workbook very quickly.
This is what your proposed summary table looks like:
[TABLE="width: 335"]
<tbody>[TR]
[TD]Aggregate[/TD]
[TD]Rank[/TD]
[TD]Rank[/TD]
[TD]Rank[/TD]
[/TR]
[TR]
[TD]Date[/TD]
[TD]Sales[/TD]
[TD]Units[/TD]
[TD]Palettes[/TD]
[/TR]
[TR]
[TD="align: right"]15/08/2013[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]22/08/2013[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]29/08/2013[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]5/09/2013[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]12/09/2013[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]19/09/2013[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]26/09/2013[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]3/10/2013[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]10/10/2013[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]17/10/2013[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]24/10/2013[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
</tbody>[/TABLE]
However I have notice the sample data you have provided does not actually have any August dates:
Here is a sample of what a pivot table was able to return after I combined your spreadsheets:
[TABLE="width: 285"]
<tbody>[TR]
[TD]Row Labels[/TD]
[TD]Palettes[/TD]
[TD]Sales[/TD]
[TD]Units[/TD]
[/TR]
[TR]
[TD]7/09/2013[/TD]
[TD="align: right"]33[/TD]
[TD="align: right"]83[/TD]
[TD="align: right"]124[/TD]
[/TR]
[TR]
[TD]13/09/2013[/TD]
[TD="align: right"]17[/TD]
[TD="align: right"]44[/TD]
[TD="align: right"]80[/TD]
[/TR]
[TR]
[TD]14/09/2013[/TD]
[TD="align: right"]2[/TD]
[TD="align: right"]13[/TD]
[TD="align: right"]36[/TD]
[/TR]
[TR]
[TD]19/09/2013[/TD]
[TD="align: right"]16[/TD]
[TD="align: right"]22[/TD]
[TD="align: right"]60[/TD]
[/TR]
[TR]
[TD]20/09/2013[/TD]
[TD="align: right"]14[/TD]
[TD="align: right"]11[/TD]
[TD="align: right"]52[/TD]
[/TR]
[TR]
[TD]21/09/2013[/TD]
[TD="align: right"]18[/TD]
[TD="align: right"]30[/TD]
[TD="align: right"]70[/TD]
[/TR]
[TR]
[TD]24/09/2013[/TD]
[TD="align: right"]29[/TD]
[TD="align: right"]81[/TD]
[TD="align: right"]238[/TD]
[/TR]
[TR]
[TD]25/09/2013[/TD]
[TD="align: right"]86[/TD]
[TD="align: right"]155[/TD]
[TD="align: right"]416[/TD]
[/TR]
[TR]
[TD]26/09/2013[/TD]
[TD="align: right"]19[/TD]
[TD="align: right"]32[/TD]
[TD="align: right"]68[/TD]
[/TR]
[TR]
[TD]27/09/2013[/TD]
[TD="align: right"]80[/TD]
[TD="align: right"]122[/TD]
[TD="align: right"]230[/TD]
[/TR]
[TR]
[TD]28/09/2013[/TD]
[TD="align: right"]12[/TD]
[TD="align: right"]33[/TD]
[TD="align: right"]56[/TD]
[/TR]
[TR]
[TD]29/09/2013[/TD]
[TD="align: right"]24[/TD]
[TD="align: right"]12[/TD]
[TD="align: right"]19[/TD]
[/TR]
[TR]
[TD]30/09/2013[/TD]
[TD="align: right"]122[/TD]
[TD="align: right"]56[/TD]
[TD="align: right"]156[/TD]
[/TR]
[TR]
[TD]1/10/2013[/TD]
[TD="align: right"]32[/TD]
[TD="align: right"]55[/TD]
[TD="align: right"]113[/TD]
[/TR]
[TR]
[TD]2/10/2013[/TD]
[TD="align: right"]516[/TD]
[TD="align: right"]381[/TD]
[TD="align: right"]837[/TD]
[/TR]
[TR]
[TD]3/10/2013[/TD]
[TD="align: right"]37[/TD]
[TD="align: right"]59[/TD]
[TD="align: right"]79[/TD]
[/TR]
</tbody>[/TABLE]
etc (the data continues on until 24th October 2013)
That is sum but I can turn that into rank with the click of button:
[TABLE="width: 364"]
<tbody>[TR]
[TD]Row Labels[/TD]
[TD]Palettes[/TD]
[TD]Sales[/TD]
[TD]Units[/TD]
[TD]Grand Total[/TD]
[/TR]
[TR]
[TD]7/09/2013[/TD]
[TD="align: right"]9[/TD]
[TD="align: right"]7[/TD]
[TD="align: right"]10[/TD]
[TD="align: right"]10[/TD]
[/TR]
[TR]
[TD]13/09/2013[/TD]
[TD="align: right"]17[/TD]
[TD="align: right"]13[/TD]
[TD="align: right"]12[/TD]
[TD="align: right"]13[/TD]
[/TR]
[TR]
[TD]14/09/2013[/TD]
[TD="align: right"]30[/TD]
[TD="align: right"]25[/TD]
[TD="align: right"]22[/TD]
[TD="align: right"]24[/TD]
[/TR]
[TR]
[TD]19/09/2013[/TD]
[TD="align: right"]18[/TD]
[TD="align: right"]21[/TD]
[TD="align: right"]16[/TD]
[TD="align: right"]18[/TD]
[/TR]
[TR]
[TD]20/09/2013[/TD]
[TD="align: right"]20[/TD]
[TD="align: right"]27[/TD]
[TD="align: right"]19[/TD]
[TD="align: right"]20[/TD]
[/TR]
[TR]
[TD]21/09/2013[/TD]
[TD="align: right"]16[/TD]
[TD="align: right"]18[/TD]
[TD="align: right"]14[/TD]
[TD="align: right"]15[/TD]
[/TR]
[TR]
[TD]24/09/2013[/TD]
[TD="align: right"]11[/TD]
[TD="align: right"]8[/TD]
[TD="align: right"]5[/TD]
[TD="align: right"]7[/TD]
[/TR]
[TR]
[TD]25/09/2013[/TD]
[TD="align: right"]5[/TD]
[TD="align: right"]5[/TD]
[TD="align: right"]2[/TD]
[TD="align: right"]2[/TD]
[/TR]
[TR]
[TD]26/09/2013[/TD]
[TD="align: right"]15[/TD]
[TD="align: right"]16[/TD]
[TD="align: right"]15[/TD]
[TD="align: right"]14[/TD]
[/TR]
[TR]
[TD]27/09/2013[/TD]
[TD="align: right"]6[/TD]
[TD="align: right"]6[/TD]
[TD="align: right"]6[/TD]
[TD="align: right"]6[/TD]
[/TR]
[TR]
[TD]28/09/2013[/TD]
[TD="align: right"]22[/TD]
[TD="align: right"]15[/TD]
[TD="align: right"]17[/TD]
[TD="align: right"]16[/TD]
[/TR]
[TR]
[TD]29/09/2013[/TD]
[TD="align: right"]12[/TD]
[TD="align: right"]26[/TD]
[TD="align: right"]28[/TD]
[TD="align: right"]23[/TD]
[/TR]
[TR]
[TD]30/09/2013[/TD]
[TD="align: right"]3[/TD]
[TD="align: right"]11[/TD]
[TD="align: right"]8[/TD]
[TD="align: right"]8[/TD]
[/TR]
[TR]
[TD]1/10/2013[/TD]
[TD="align: right"]10[/TD]
[TD="align: right"]12[/TD]
[TD="align: right"]11[/TD]
[TD="align: right"]11[/TD]
[/TR]
[TR]
[TD]2/10/2013[/TD]
[TD="align: right"]1[/TD]
[TD="align: right"]1[/TD]
[TD="align: right"]1[/TD]
[TD="align: right"]1[/TD]
[/TR]
[TR]
[TD]3/10/2013[/TD]
[TD="align: right"]8[/TD]
[TD="align: right"]10[/TD]
[TD="align: right"]13[/TD]
[TD="align: right"]12[/TD]
[/TR]
</tbody>[/TABLE]
Or I can sum by Platform (your worksheet name) and month
[TABLE="width: 397"]
<tbody>[TR]
[TD]Worksheet[/TD]
[TD]Date[/TD]
[TD]Palettes[/TD]
[TD]Sales[/TD]
[TD]Units[/TD]
[TD]Grand Total[/TD]
[/TR]
[TR]
[TD]Platform 1[/TD]
[TD]Sep[/TD]
[TD="align: right"]295[/TD]
[TD="align: right"]392[/TD]
[TD="align: right"]1149[/TD]
[TD="align: right"]1836[/TD]
[/TR]
[TR]
[TD][/TD]
[TD]Oct[/TD]
[TD="align: right"]639[/TD]
[TD="align: right"]395[/TD]
[TD="align: right"]1011[/TD]
[TD="align: right"]2045[/TD]
[/TR]
[TR]
[TD]Platform 2[/TD]
[TD]Sep[/TD]
[TD="align: right"]76[/TD]
[TD="align: right"]181[/TD]
[TD="align: right"]295[/TD]
[TD="align: right"]552[/TD]
[/TR]
[TR]
[TD][/TD]
[TD]Oct[/TD]
[TD="align: right"]190[/TD]
[TD="align: right"]348[/TD]
[TD="align: right"]536[/TD]
[TD="align: right"]1074[/TD]
[/TR]
[TR]
[TD]Platform 3[/TD]
[TD]Sep[/TD]
[TD="align: right"]22[/TD]
[TD="align: right"]46[/TD]
[TD="align: right"]59[/TD]
[TD="align: right"]127[/TD]
[/TR]
[TR]
[TD][/TD]
[TD]Oct[/TD]
[TD="align: right"]89[/TD]
[TD="align: right"]257[/TD]
[TD="align: right"]309[/TD]
[TD="align: right"]655[/TD]
[/TR]
[TR]
[TD]Platform 4[/TD]
[TD]Sep[/TD]
[TD="align: right"]3[/TD]
[TD="align: right"]4[/TD]
[TD="align: right"]21[/TD]
[TD="align: right"]28[/TD]
[/TR]
[TR]
[TD][/TD]
[TD]Oct[/TD]
[TD="align: right"]53[/TD]
[TD="align: right"]83[/TD]
[TD="align: right"]144[/TD]
[TD="align: right"]280[/TD]
[/TR]
[TR]
[TD]Platform 5[/TD]
[TD]Sep[/TD]
[TD="align: right"]76[/TD]
[TD="align: right"]71[/TD]
[TD="align: right"]81[/TD]
[TD="align: right"]228[/TD]
[/TR]
[TR]
[TD][/TD]
[TD]Oct[/TD]
[TD="align: right"]198[/TD]
[TD="align: right"]284[/TD]
[TD="align: right"]308[/TD]
[TD="align: right"]790[/TD]
[/TR]
[TR]
[TD]Grand Total[/TD]
[TD][/TD]
[TD="align: right"]1641[/TD]
[TD="align: right"]2061[/TD]
[TD="align: right"]3913[/TD]
[TD="align: right"]7615[/TD]
[/TR]
</tbody>[/TABLE]
I know this is not what you asked for but it a potential is solution in case an MVP can't help you (I am no where near as good as those guys). And at least it keeps your post visible - someone else might see it and offer a better solution.