I always had problems with that annoying “NaN” in SSRS, I used to run around it using IIF or REPLACE and ROUND, but finally I decided not to give up and find a neater solution for that particular report. Reading more about the IIF function @ http://msdn.microsoft.com/en-us/library/27ydhh0d%28vs.71%29.aspx At the remarks section, they say “The expressions in the argument list can include function calls. As part of preparing the argument list for the call to IIf , the Visual Basic compiler calls every function in every expression. This means that you cannot rely on a particular function not being called if the other argument is selected by Expression .” Anyway to cut my story short, if you have a function like: =IIF(Lookup(Fields!ADM_DR_ID.Value, Fields!ADM_DR_ID.Value, Fields!ID2010.Value, "LOS") = nothing, "0" , Lookup(Fields!ADM_DR_ID.Value, Fields!ADM_DR_ID.Value, Fields!ID2010.Value, "LOS")) It’s not going to work. The right way is to avoid dividi...