Hi Rick,
I think ideally you would want to amend the formula in E38 so it doesn't return a #DIV/0! error either. To do this you would use a similar IF() formula construction to the one already mentioned.
But, if you want an error to displayed in E38 then you could cater for it by using a formula like:
=IF(AND(B38<>0,ISNUMBER(E38)),(E38-B38)/B38,0)
Hope that helps...