Dim ds1 As Double = CDbl(e.Form.Controls("D1").Value) + CDbl(e.Form.Controls("D2").Value)
Dim ds2 As Double = CDbl(e.Form.Controls("D2").Value) + CDbl(e.Form.Controls("D3").Value)
e.Form.Controls("D5").Value = ds1 * ds2 * CDbl(e.Form.Controls("D4").Value)