I've hit a bit of snag in a logbook that I'm trying to create Excel. Essentially I have an array that I would like to act on an 3D reference, but alas Excel doesn't seem to allow this. Is there a way round this?

The formula in question is:

(SUMPRODUCT(--('Sheet1'!$G$2:$G$500=A8),--($H$3<='Sheet1'!$A$2:$A$500),--($L$3>='Sheet1'!$A$2:$A$500)))

Where it says sheet1, I'd ideally like something along the lines of 'Sheet1:Sheet10'!. I'd also want to link this to an external workbook, but I thought I'd see if anyone can help with this connundrum first!

Thanks for taking the time to read this, and thanks in advance for anyone who can shed any light on this!

Simon