Cumulative Sum total matching cell reference with hlookup or index

[Legacy 319150]

Hi - i hoping someone out there can help me

I'm looking for a Cumulative formula sumif/then lookup

I'd like to have my current stock in 1 cell (A3) the formula in B3, Data in C3:H3, and dates the stock runs out in C1:H1

The formula..
Cumulative Sum C3:H3 but when C3+D3+E3 etc... = A3 (or the closest number to) hlookup/index The corresponding Row 1 to tell me when to order stock

Example...

[TABLE="width: 535"]
<TBODY>[TR]
[TD]Current Stock</SPAN>[/TD]
[TD]Date</SPAN>[/TD]
[TD="align: right"]01-Apr</SPAN>[/TD]
[TD="align: right"]02-Apr</SPAN>[/TD]
[TD="align: right"]03-Apr</SPAN>[/TD]
[TD="align: right"]04-Apr</SPAN>[/TD]
[TD="align: right"]05-Apr</SPAN>[/TD]
[TD="align: right"]06-Apr</SPAN>[/TD]
[/TR]
[TR]
[TD][/TD]
[TD="colspan: 2"]Order Date</SPAN>[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]60</SPAN>[/TD]
[TD="align: right"]0</SPAN>[/TD]
[TD="align: right"]10</SPAN>[/TD]
[TD="align: right"]20</SPAN>[/TD]
[TD="align: right"]10</SPAN>[/TD]
[TD="align: right"]9</SPAN>[/TD]
[TD="align: right"]15</SPAN>[/TD]
[TD="align: right"]7</SPAN>[/TD]
[/TR]
</TBODY><COLGROUP><COL><COL span=7></COLGROUP>[/TABLE]


C3:F3 = 49... So F3 is the last site i have the full amount of stock for so return the date in F1 (04-Apr)
If i used C3:G3 it would have = 64 so would equate to more stock than i have so is no good to me.

Hopefully i have explained this sufficiently to you?! The actual data is may hunderds of rows / columns so forecasting stock requirements is a pain in the neck - i need something like the above to assist with a repetative task and daily current stock holding variances.

Thank you in advance for any suggestions (other than get someone else at work to do this!)

Regards, Darren