The logic of your formula is "If there is an error looking in book2,
then look in book1". You don't say to look in book 2 if there is no
error, so you might like to amend your formula to:

=IF(ISNA(VLOOKUP(P8,'[workbook2.xls]tabname'!$C:$S,
17,FALSE)),VLOOKUP(P8,'tabname in workbook1'!$A:$F,
5,FALSE),VLOOKUP(P8,'[workbook2.xls]tabname'!$C:$S,17,FALSE))

However, this does not check for the item being in book1 - it assumes
it is there, and if not the formula will return #N/A.

A more generic approach would be:

=IF(ISNA(vlookup_1),IF(ISNA(vlookup_2),"not
present",vlookup_2),vlookup_1)

Looks in table_1 first and returns from there if present, otherwise
looks in table_2 and returns from there if present. If absent from
both, then the error message is returned.

Hope this helps.

Pete

On Feb 4, 4:00*pm, steph wrote:
I have a new problem I need help with. *I am trying to look up a value found
in workbook #1. *I need to lookup the value in workbook #2 and, if it's not
found there, then lookup the value in a different tab of workbook #1. *Here
is what I have so far.

equalIF(ISNA(VLOOKUP(P8,'[workbook2.xls]tabname'!$C:$S,17,FALSE)),VLOOKUP(P*8,'tabname in workbook1'!$A:$F,5,FALSE))

The 2nd part of the formula works fine as the lookup returns the appropriate
P8 value from the tab in workbook 1 when it is not found in workbook2. *
However, when the value IS found in workbook2, it returns a value of FALSE,
not the appropriate lookup value.

Should I be using a different IS function? *Any assistance would be greatly
appreciated!!
--
Thanks so much!