I'm using the following formula

=INDEX(QB6!$A:$A,MATCH($B31,QB6!$B:$B,0))

This generally works, but occasionally it doesn't find a match on page QB6,
in which case I get the #N/A! error. Instead of getting that error, I would
like to force a value into that cell (a defined number).

I'm trying to tweak it using the IF ISNA commands but just can't seem to get
it right. Thanks in advance