Problem with the summate in set analysis

[geogou1973]

Hello,

i have the following expression that summate (if the weighed item (QTY_VAR) = 0) the fragmentary item (QTY) +

(if the weighed item (QTY_VAR) <> 0) the weighed item (QTY_VAR) and all that multiplies with the COST

(sum({<ITEM={"=sum(QTY_VAR)=0"}>} QTY)
+sum({<ITEM={"=sum(QTY_VAR)<>0"}>} QTY_VAR))*COST

The chart is configurable , the user choices fields from a table and the chart show the fields e.g if i choose the ITEM the formula gives the correct results but if i choose the STORE the results are different .

How can i have the correct results for all the fields as the field ITEM ;

Thank you in advanced.