Conditional Sum for Amount

Hello,

I am new to Report Builder and I am seeking assistance to write an expression that is a conditional sum.

I am attempting to sum the “Check/EFT Amount” values, if the “Check/EFT Number” is between the first and last “Check/EFT Number” values of the semantic model dataset. The first and last “Check/EFT number” values are dynamic value and will change based on the provided parameter date value. The Starting query below is the query from SAP business objects that I am attempting to replicate in Report Builder.

The Error I receive is “uses a First, Last or Previous aggregate in an outer aggregate.  These aggregate functions cannot be specified as nested aggregates.”

For reference, I have attempted to use Min and Max, which avoids the error but the resulting values are different than First and Last. Therefore I do not receive the expected sum amount. I have also attempted a custom code solution with no success.

Starting Query (SAP):

 =Sum([DISB Actg Line Check Amt])

Where ([DISB Hdr Check No] >= [Var - Begin Check Number ] And [DISB Hdr Check No] <= [Var - End Check Number])

My Report Builder Expression:

=Sum(IIf(Fields!Check_EFT_Number.Value >= First(Fields!Check_EFT_Number.Value) And Fields!Check_EFT_Number.Value <= Last(Fields!Check_EFT_Number.Value), Fields!Check_EFT_Amt.Value, 0))