This code in the forms BeforeUpdate event does what you asked for:
Code:
Private Sub Form_BeforeUpdate(Cancel As Integer) If Me.one = 0 And Me.two = 0 And Me.three = 0 Then
MsgBox "this is your msg"
Cancel = True 'This stops the form from updating
End If
End Sub
However, if any of the boxes a ZLS you would need this code:
Code:
Private Sub Form_BeforeUpdate(Cancel As Integer) If Nz(Me.one, 0) = 0 And Nz(Me.two, 0) = 0 And Nz(Me.three, 0) = 0 Then
MsgBox "this is your msg"
Cancel = True 'This stops the form from updating
End If
End Sub
Edit:
Sorry. didn't notice that Linq had already replied