การ count จำนวน และ การคำนวณข้อมูล ใน gridview asp.net VB

Private total As Decimal = 0
Protected Sub gvPurchaseOrderDetail_RowDataBound(sender As Object, e As GridViewRowEventArgs)
	If e.Row.RowType = DataControlRowType.DataRow Then
		Dim lblPrice As Label = DirectCast(e.Row.FindControl("lblPrice"), Label)
		Dim price As Decimal = Convert.ToDecimal(DataBinder.Eval(e.Row.DataItem, "UnitPrice")) * Convert.ToDecimal(DataBinder.Eval(e.Row.DataItem, "OrderQty"))
		lblPrice.Text = price.ToString()
		total += price
	End If
	If e.Row.RowType = DataControlRowType.Footer Then
		Dim lblTotal As Label = DirectCast(e.Row.FindControl("lblTotal"), Label)
		lblTotal.Text = total.ToString()
	End If
End Sub

 <asp:BoundField DataField="expect" HeaderText="ค่าคาดหวัง" 
                    SortExpression="expect" />
                <asp:BoundField DataField="Expr1" HeaderText="คะแนนที่ได้" ReadOnly="True" 
                    SortExpression="Expr1" DataFormatString="{0:0.00}" />
                <asp:BoundField DataField="Expr2" HeaderText="%ต่าง" ReadOnly="True" 
                    SortExpression="Expr2" DataFormatString="{0:0.0%}" />
            </Columns>