"Robbyn" wrote...
....
Why does the following formula work:

=IF(ISBLANK(VLOOKUP($B$1,Database,217,0)),"",
VLOOKUP($B$1,Database,217,0))

But this one doesn't (I get a #REF error):

=IF(ISBLANK(VLOOKUP($B$1,Database,218,0)),"",
VLOOKUP($B$1,Database,218,0))

This is what would happen if the range named Database spanned only 217
columns.