Oops, just noticed I used IIf rather than If and Or rather than Else....
If Me.txtNumber = 0 Then
Me.ImageA.Visible = True
Me.ImageB.Visible = False
Else
Me.ImageA.Visible = False
Me.ImageB.Visible = True
End If
or you can use:
Me.ImageA.Visible = (Me.txtNumber = 0)
Me.ImageB.Visible = (Me.txtNumber <> 0)