Formula in Calculated Dimension

[#1]

Dear Experts,

I am using the below formula in the calculated dimension of a pivot table and getting "// Error in calculated dimension"

"if(sum(Stock_Qty)>0,If((sum(Stock_Qty)/AvrgSales)>$(VMonths),sum(Stock_Qty) - ($(VMonths) * AvrgSales),))"

Any help

[#2]

Yes each ItemName has one AvrgSales loded in Qlikview this value is unique by ItemName and dose not change. Actually it is an estimation of the sales.

VMonths is defined using a slider in QlikView.

You mean " by stray?

In my formula I am using sum many times with each sum I have to use aggr()?