ช่วยหน่อยนะครับ ติดเรื่อง run ตัวเลข นิดเดียว VB.NET

Sql = "select * from t_friend order by f_id desc"
        Da_Friend.MissingSchemaAction = MissingSchemaAction.AddWithKey
        Da_Friend.SelectCommand = New OleDbCommand(Sql, Con)
        Try
            Da_Friend.Fill(Ds_Friend, "auto_friend")
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
        Dim DrMax As DataRow : Dim id_friend As String
        If Ds_Friend.Tables("auto_friend").Rows.Count <= 0 Then
            id_friend = "00001"
        Else
            DrMax = Ds_Friend.Tables("auto_friend").Rows(0)
            Dim W, Po As String : Dim Num As Integer
            W = DrMax("f_id").ToString()
            Po = Mid(W, 2, Len(W))
            Num = CInt(Po) + 1
            id_friend = String.Format("{1:00000}", "", Num)
        End If
        TxtId.Text = "F" & id_friend