I am writing a report with a column that calculates year over year comps in sales. The problem I am having is that we do not have any sales history that dates before the beginning of this year. I am using the formula below to calcute the percent change but am getting NaN and Inf errors due to the fact that there is zero in the denominator. Is there a way to write this formula to exclude those, perhaps an iif statement?

=(SUM(Fields!MTDInvoiced.Value)-SUM(Fields!PYMTDInvoiced.Value))/SUM(Fields!PYMTDInvoiced.Value)