Report Field Calculation based on start date

[Tarbuza]

I have following field in my report

Action
Start Data
End Date
Qty
2003 : Formula is Qty*5, if start date falls in 2003 then Qty*6
2004 : Formula is Qty*12, if start date falls in 2004 then Qty*13
2005 : Formulat is Qty*12, if start date falls in 2005 then Qty*13

I started something like this but I am stuck as I am new to Access VBA. Please help.

Private Sub Detail_Format(Cancel As Integer, FormatCount As Integer)
If Not IsNull(Me. START_DT) Then

Select Case Year(Me. START_DT)
Case 2002

Case 2004

Case 2005

Case 2006

End Select
End If
End Sub