Hello,
I simply need to lookup 2 cells on another sheet and add them together
without producing any errors if one or both of them is blank. I am using:

=SUM(IF(ISNUMBER(LOOKUP($G2,Technicians!A:A,Techni cians!BG:BG)),(LOOKUP($G2,Technicians!A:A,Technici ans!BG:BG)),""),(IF(ISNUMBER(LOOKUP($G2,Technician s!A:A,Technicians!BH:BH)),(LOOKUP($G2,Technicians! A:A,Technicians!BH:BH)),"")))

This will add the numbers together if there is a number in each cell, but I
get the #VALUE error if one of them is blank. The (IF ISNUMBER) portion of it
was intended to avoid errors, but is not working here. Any help appreciated...
thanks,
Robert