How do do a lookup BeforeUpdate Event 1

[netrusher]

I have a form that allows a person to click a dropdown
ComboBox and select a training class they would like to
attend. I would like to do a BeforeEvent lookup to see
if they have already selected this class. If they have
I would like a pop-up to appear saying you have already
selected this class. Can anyone give me an example of how
this could be done with a look-up?
Fields involved are:
ClockNbr
FirstName
LastName
ClassSubject
Table involved is MasterInputTbl

 

[LisaWay]

Would this do the trick?

Private Sub MyCombo_BeforeUpdate(Cancel As Integer)
    If Not IsNull(DFirst("ClockNbr", "MasterInputTbl", _
        "[FirstName]='" & Me![FirstName] & _
        "' And [LastName]='" & Me![LastName] & _
        "' And [ClassSubject]='" & Me![MyCombo] & "'")) Then
        Cancel = True
        MsgBox "You have already selected this class."
    End If
End Sub

 

[netrusher]

LisaWay,

Blessings to you!

That works great. Many Thanks.