Sorry I accidentally hit the post button before I completed my question. I
am having a problem with the formula below when there is a zero in one of the
lookup cells in the named region Period1 and Period2. I am not sure how to
modify the formula so that when those cells are zero or blank it doesn't
return an error message.

"hkslater" wrote:

=ROUNDDOWN((VLOOKUP($D9,Period1,VLOOKUP(I$6,Column s,3,FALSE),FALSE)/VLOOKUP($D9,Period1,3,FALSE)*$E9)+(VLOOKUP($D9,Per iod2,VLOOKUP(I$6,Columns,3,FALSE),FALSE)/VLOOKUP($D9,Period2,3,FALSE)*$F9),0)