Shortening Formula ? Using a nested indirect

[PureBluff]

Hi,

I have a formula, which works fine, however I'd like to shorten it ... If anyone could direct me if it's at all possible?

=SUMIF(INDIRECT("'H:\A\Oggy\Project\Loading\"&TEXT(B1,"mm mmmm yyyy")&"\["&TEXT(B1,"dd-mm-yyyy")&".xls]WA'!ag:ag"),$A4,INDIRECT("'H:\A\Oggy\Project\Loading\"&TEXT(B1,"mm mmmm yyyy")&"\["&TEXT(B1,"dd-mm-yyyy")&".xls]WA'!o:o"))

Now, I wish to (end result) use this formula on B1, C1, D1, E1, F1 in the same formula, but as you can appreciate it'll become fairly large - was hoping I could insert 'H:\A\Oggy\Project\Loading\"&TEXT(B1,"mm mmmm yyyy")&"\["&TEXT(B1,"dd-mm-yyyy")&".xls as a defined name but I've had no luck with that (or my syntax afterwards is wrong!)

Limited to Excel 2003, hence wanting to keep the formula length down.

Thanks

 

[PureBluff]

No-one able to offer a suggestion?