If txtpof.Text <> "" And txtmat.Text <> "" Then

 cmd = New OleDbCommand("select N_Paiement,Nom,Prenom,Niveau,Date_Début,Date_fin,montant from  paiement,adhérent  where N_Inscription=N_Ins and paiement.Date_Début <=" & txtdebut.Text & "and paiement.date_fin >=" & txtfin.Text & "", con)

            dtr = cmd.ExecuteReader
            Dim tab As New DataTable
            tab.Load(dtr)
            DataGridView1.DataSource = tab
        End If