update and insert problem

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Try
            con = New OleDbConnection(cs)
            con.Open()
            Dim ct As String = "select ProductModel from StockDisplay where ProductModel=@find"
            cmd = New OleDbCommand(ct)
            cmd.Connection = con
            cmd.Parameters.Add(New OleDbParameter("@find", System.Data.OleDb.OleDbType.VarChar, 255, "ProductModel"))
            cmd.Parameters("@find").Value = Me.ProductModelComboBox.Text
            rdr = cmd.ExecuteReader()

            If rdr.Read Then
                con = New OleDbConnection(cs)
                con.Open()
                Dim myQty As Integer
                Integer.TryParse(Me.QtyTextBox.Text, myQty)
                Dim cb1 As String = "update StockDisplay set Qty = Qty + " & myQty & " where Product= '" & Me.ProductModelComboBox.Text & "'"
                cmd = New OleDbCommand(cb1)
                cmd.Connection = con
                cmd.ExecuteReader()
            Else
                con = New OleDbConnection(cs)
                con.Open()
                Dim cb2 As String = "insert into StockDisplay(ProductModel,Qty) VALUES (@d1,@d2)"
                cmd = New OleDbCommand(cb2)
                cmd.Connection = con

                cmd.Parameters.Add(New OleDbParameter("@d1", System.Data.OleDb.OleDbType.VarChar, 100, "ProductModel"))
                cmd.Parameters.Add(New OleDbParameter("@d2", System.Data.OleDb.OleDbType.VarChar, 100, "Qty"))

                cmd.Parameters("@d1").Value = Me.ProductModelComboBox.Text
                cmd.Parameters("@d2").Value = Me.QtyTextBox.Text

                cmd.ExecuteReader()
                If con.State = ConnectionState.Open Then
                    con.Close()
                End If
            End If
            con.Close()
            con.Close()

        Catch ex As Exception
            MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try
    End Sub