Substituting cells formula???

I thought I had it. I tried reversing the formula:

=IF(ISNUMBER(N8),N8,IF(ISNUMBER(L8),L8,0))

In this scenario it shows N8, but if the cell is empty it does not show L8

=IF(ISNUMBER(L8),L8,IF(ISNUMBER(N8),N8,0))

In this scenario it shows L8, but if the cell is empty it does not show N8

Maybe I'm missing something here.

Thanks again for the help... Oh, I'm using Excel 2007, just in case.

OS