[AccessD] code help please

It is almost Midnight here
What is wrong with the following code please?

Private Sub ReportFooter_Format(Cancel As Integer, FormatCount As Integer)
    if isnull me.txtPONptes then   < This is null line is the trouble maker
        Me.lblPONotes.Visible = False
        Me.txtPONptes.Visible = False
    End If
    
End Sub

JOE HECHT
LOS ANGELES CA 
 jmhla at earthlink.net