อยากทราบวิธีการหาผลรวมรายได้จาก Gridview ได้อย่างไร

Private Sub myGridView_RowDataBound(sender As Object, e As GridViewRowEventArgs)
'*************************'
'*************************'
'*************************'

'*** CustomerID ***'
Dim lblCustomerID As Label = CType(e.Row.FindControl("lblCustomerID"),Label)
IF Not IsNothing(lblCustomerID) Then
lblCustomerID.Text = e.Row.DataItem("CustomerID")
End IF

'*** Email ***'
Dim lblName As Label = CType(e.Row.FindControl("lblName"),Label)
IF Not IsNothing(lblName) Then
lblName.Text = e.Row.DataItem("Name")
End IF

'*** Name ***'
Dim lblEmail As Label = CType(e.Row.FindControl("lblEmail"),Label)
IF Not IsNothing(lblEmail) Then
lblEmail.Text = e.Row.DataItem("Email")
End IF

'*** CountryCode ***'
Dim lblCountryCode As Label = CType(e.Row.FindControl("lblCountryCode"),Label)
IF Not IsNothing(lblCountryCode) Then
lblCountryCode.Text = e.Row.DataItem("CountryCode")
End IF

'*** Budget ***'
Dim lblBudget As Label = CType(e.Row.FindControl("lblBudget"),Label)
IF Not IsNothing(lblBudget) Then
lblBudget.Text = FormatNumber(e.Row.DataItem("Budget"),2)
End IF

'*** Used ***'
Dim lblUsed As Label = CType(e.Row.FindControl("lblUsed"),Label)
IF Not IsNothing(lblUsed) Then
lblUsed.Text = FormatNumber(e.Row.DataItem("Used"),2)
End IF
End Sub