Is There Away to Set a Default Value for a Combo Box from a Procedure?

[quest4]

I have a form where, only from this procedure, I go to a combo box, I can use these default values in the combo box, which the procedure is setting. Here is the procedure:
Private Sub WorkDay1_AfterUpdate()

DoCmd.GoToControl "WorkDay1Reason"

If WorkDay1 > 0 Then
WorkDay1ReasonCombo.ItemData (6)
Else: WorkDay1ReasonCombo.ItemData (0)

End If
End Sub
Currently I am getting a err 424 when I run it. Any suggestions on how to get this to work? The default on the property sheet is not a viable solution because I want the normal default to be blank. Thanks in advance to anyone who helps out.