Find last row in range using INDEX

[skysurfer]

Hi,

How do I modify the following array formula to read a range that starts in cell C18 and extends down rows and across columns that are numbers referenced in two cells?

Here's the formula now (which returns the last row containing any type of data in a specified range):

={(MAX((C$18:L28<>"")*ROW(C$18:L28)))-ROW(C$18:L28)+1}

What I need is to have L28 replaced by INDEX (I think) that references cell A1 containing the last row number and cell A2 containing the last column number in the range to be searched.

Thanks,

Lawrence