My mind is still boggling over multiple people using a single email address...but anyway...I've done this kind of thing before, in my early days, and while it's an unorthodox approach (I've never seen it done this way, anywhere else) it works just fine!
Replacing TableName, FirstName, LastName, and EmailAddress with the actual names of your Table, Fields and Textboxes:
Code:
Private Sub Form_BeforeUpdate(Cancel As Integer)
If DCount("*", "TableName", "FirstName & LastName & EmailAddress = '" & Me.FirstName & Me.LastName & Me.EmailAddress & "'") > 0 Then
Cancel = True
MsgBox "This Combination Already Exists!"
Me.Undo
End If
End Sub
Linq ;0)>
The problem with making anything foolproof...is that fools are so darn ingenious!
All posts/responses based on Access 2003/2007