Hi Ryan
The short answer is yes.
If you want to sum a calculated field then you repeat the original formula inside a Sum() function, for example, if your original formula in the calculated field is =[Field1]*[Field2] then the control source for the sum of the calcualted field will be =Sum([Field1]*[Field2]) in the report or section footer.
If you want a conditional sum, then your formula might look like something like this : =Sum(Iif([Field1]>0,[Field1],0))
I trust I understood your question correctly?
Andrew