Just for interest, logical functions such as ISBLANK return TRUE or FALSE, which can be translated into their numeric equivalents of 1 or 0 quite easily by multiplying by -1 twice, like this:
=--ISBLANK(<cell with value>)
( the "--" does the multiplying by -1 twice )
Cheers, Glenn.
Did you hear about the literalist show-jumper? He broke his nose jumping against the clock.