Here is the formula:
=IF(ISNA(VLOOKUP($B63,Exp_100,J$32,FALSE)),0,VLOOKUP($B63,Exp_100,J$32,FALSE)) - which works fine except if I want to add another tab Exp_xxx, I cannot locate the place where the table array resides so that I can adjust it to include "Exp_XXX".

There are many, many tabs in this particular workbook, and so far I do not see the list from which the source of the table_array originates.