I am using a IF ISNA with two different vlookups.

=IF(ISNA(VLOOKUP(A42963,LL_Cost,2,0)),GETPIVOTDATA ("Cost",Cost,"Analyte",Sheet1!F42963,"Laboratory", Sheet1!I42963),VLOOKUP(A42963,LL_Cost,2,0))

This formula works great, except that the cells that don't find anything in
either table return a #REF and I want this value to be zero. Is there a way
to do this.