Visual Basic.NET - Al seleccionar un Elemento de un ListBox que se muestren datos en un TextBox

Sub buscanombre2( ByVal sql As String)

    dgvExcel.DataSource = Nothing

    Try

        Dim ad As New NpgsqlDataAdapter(sql, conexion)

        Dim dt As New DataTable

        Dim ds As New DataSet

        conexion.Open()

        ad.Fill(dt)

        ad.Fill(ds)

        conexion.Close()

        If ds.Tables(0).Rows.Count > 0 Then

            If IsDBNull(ds.Tables(0).Rows(0).Item(0)) Then

            Else

                Dim filasdgventas As Integer = ds.Tables(0).Rows.Count

                Form3.TextBox2.Text = ds.Tables(0).Rows(0).Item(0)

                Form3.TextBox7.Text = ds.Tables(0).Rows(0).Item(1)

                Form3.TextBox8.Text = ds.Tables(0).Rows(0).Item(2)

            End If

        End If

        dgvExcel.DataSource = dt

    Catch ex As NpgsqlException

        MessageBox.Show(ex.Message)

    End Try

End Sub