Running total miss calculation having two unbound columns

See more:

C#

DevExpress

Running total is been miss calculated when i have more than one unbound column to display the running total of certain products.

Displaying the running total of a single products, it is perfectly working, but when i add more unbound columns, the results are not not properly calculated.

for instance for a single product A:

Running total is perfectly calculated
Prod A Cum A
1 1
2 3
3 6

for instance for two products A and B this is the result i get:

Prod A Prod B Cum A Cum B
1 2 3 3
2 4 9 9
3 6 18 18


Any Suggestion?

Regards

What I have tried:

here below is the code i used to calculate the Running total for a single product A:

 private void ProdgridView_CustomUnboundColumnData(object sender, DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs e)
        {
            GridView view = sender as GridView;

            if (e.Column.FieldName == "ACumProd" & e.IsGetData )
            {
                decimal val = 0;
                for (int i = 0; i <= e.ListSourceRowIndex; i++)
                {
                    val = val + (decimal)view.GetRowCellValue(i, view.Columns["ProdA"]);
                    
                }
                e.Value = val;
            }

And For two products A and B 

private void ProdgridView_CustomUnboundColumnData(object sender, DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs e)
        {
            GridView view = sender as GridView;

            if (e.Column.FieldName == "ACumProd" & e.IsGetData || e.Column.FieldName == "BCumProd" & e.IsGetData)
            {
                decimal val = 0;
                for (int i = 0; i <= e.ListSourceRowIndex; i++)
                {
                    val = val + (decimal)view.GetRowCellValue(i, view.Columns["ProdA"]);
val = val + (decimal)view.GetRowCellValue(i, view.Columns["ProdB"]);
                    
                }
                e.Value = val;
            }