Increment Field Values

Hi

I have a numeric field called FileNo and an autonumber field called FileID in a table called tblFile.
I also have a lookup numeric field called FileTypeID (with values 1 or 2 or 3) on another table called tblFileType.

I need the value of FileNo which I am showing on a Form frmFile to change dependant on the value of the FileTypeID
i.e. If FileTypeID = 1 FlieNo should start at 100
If FileTypeID = 2 FileNo should start at 200
If FileTypeID = 3 FileNo should start at 300
Then when I create a new record I need to increment by 1 the value of FileNo according to the FileTypeID

I've setup a button and attached this code to its onclick event but it only works as long as I don't change the FileTypeID


Dim B As Integer
Dim H As Integer
Dim N As Integer

Do While FileID > 0
DoCmd.GoToRecord,,acPrevious
If FileTypeID = 1 Then
B = FileNo
Else
If FileTypeID = 2 Then
H = FileNo
Else
If FileTypeID = 3 Then
N = FileNo
End If
End If
End If
Loop

DoCmd.GoToRecord,,acLast
If FileType = 1 Then
FileNumber = B + 1
Else
If FileType = 2 Then
FileNumber = H + 1
Else
If FileType = 3 Then
FileNumber = N + 1
End If
End If
End If


ViRi