Filters, keys and grouping

On my report I loop through the Customer table, then through the Value Entry Table where Source No. = Cust."No."

The Key on my Value Entry table is setup to be <"Source No.","Document No.","Item No.">, grouping is done on "Item No.", so on the report the total for the item per document per customer is printed.

When the user filters on "Value Entry"."Posting Date", it should not print the grouped line if for that document in that period, the "Sales Amount (Actual)" is zero. If it is not zero, find the entries of that document that fall outside of the filter and do your calculations.

The Report works fine... Except it takes AGES to complete, because of the keys and the filters that are set in code on the data item. I can't change the key on the data item because of the grouping. I can't find any other way to do it... ](*,) ](*,)