show message if item is not matched

Hello 

I  try to  show  message  when  I  write  item in combobox1  should match with column B in sheet . if  the  item is  not  matched when write  in combobox1 ,then should  show  the  message and  should  clear the  combobox1 after close  message 

Private Sub ComboBox1_Change()

    Dim ws As Worksheet, rng As Range, cb
    Set ws = Sheets("sheet1")
   cb= Me.ComboBox1.Value
    If cb<> "" Then
        Set rng = ws.Columns(2).Find(cb, LookAt:=xlWhole)
        If rng <> cb Then
        MsgBox "not matched"
    End If
 Me.ComboBox1.Value=""

any chance  to  do  that.,please?