Is this possible?

Hi Folks
Forgive a very rusty VB4/5 sometime coder trying to catch up on the .net art, for a possibly stupid question.
I have been playing around with small coding tasks as a sort of self inflicted training course, and thought that this should be possible:-
To loop through a process that creates the capital letters of the alphabet and then numbers them, as it does so, to write them as entries to a MYSQL table, i.e. A1, B2 etc.
I thought the logic through and cobbled together a procedure which runs fine once then just bombs out, please see the code below. I think that I have either made a classic schoolboy mistake, or this is just confirmation that my old grey cells have finally packed their bags and I'm now flying solo!!
Any help or guidance greatly appreciated

Code

 Private Sub btnSeed_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSeed.Click

        Dim conn As New MySqlConnection
        Dim myCommand As New MySqlCommand
        Dim myConnectionString As String

        Dim iCount As Integer
        Dim StrChar As String
        Dim sdNum As Integer

        StrChar = "@"
        sdNum = 0
      
        For iCount = 1 To 26
            StrChar = Chr(Asc(StrChar) + 1)
            sdNum = sdNum + 7

            myConnectionString = "server=localhost;User ID=Tester;Password=Tester;Database=Test"

            conn.ConnectionString = myConnectionString

            myCommand.Connection = conn

            myCommand.CommandText = "INSERT INTO seed_number(StartLetter, SeedNo) VALUES(?StartL, ?sedNum)"

            myCommand.Parameters.Add("?StartL", StrChar)
            myCommand.Parameters.Add("?sedNum", sdNum)
           
            Try
                conn.Open()
                myCommand.ExecuteNonQuery()
                conn.Close()

            Catch ex As MySqlException
                MsgBox("There was an error updating the database: " + ex.Message)

            End Try

        Next

    End Sub

Best Regards

Alex