อยากทราบการบวกค่าในคอลัมภ์ ภายใน Gridview ต้องทำยังไงครับ

  Protected Sub GridView1_RowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles GridView1.RowDataBound
        If e.Row.RowType = DataControlRowType.DataRow Then
            ' add the UnitPrice and QuantityTotal to the running total variables
            sumcountall += Convert.ToInt32(DataBinder.Eval(e.Row.DataItem, "countall"))
            sumcountInprocess += Convert.ToInt32(DataBinder.Eval(e.Row.DataItem, "countInprocess"))
            sumcountreject += Convert.ToInt32(DataBinder.Eval(e.Row.DataItem, "countreject"))
            sumcountapprove += Convert.ToInt32(DataBinder.Eval(e.Row.DataItem, "countapprove"))
        ElseIf e.Row.RowType = DataControlRowType.Footer Then
            e.Row.Cells(0).ColumnSpan = 3
            e.Row.Cells(0).HorizontalAlign = HorizontalAlign.Center
            e.Row.Cells(0).Text = "รวม :"
            ' for the Footer, display the running totals
            e.Row.Cells(1).Text = sumcountall.ToString()
            e.Row.Cells(2).Text = sumcountInprocess.ToString()
            e.Row.Cells(3).Text = sumcountreject.ToString()
            e.Row.Cells(4).Text = sumcountapprove.ToString()
            e.Row.Cells(1).HorizontalAlign = HorizontalAlign.Center
            e.Row.Cells(2).HorizontalAlign = HorizontalAlign.Center
            e.Row.Cells(3).HorizontalAlign = HorizontalAlign.Center
            e.Row.Cells(4).HorizontalAlign = HorizontalAlign.Center
            e.Row.Cells(5).Visible = False
            e.Row.Cells(6).Visible = False
            e.Row.Font.Bold = True
        End If
    End Sub