Try putting the code below before this line:userCreateStatus = UserController.CreateUser(objNewUser)

Dim sConnStr As String = {MyConnectionString}
Dim cnBKTest As New SqlConnection(sConnStr)
Dim cmdTest As New SqlCommand("NameofYourStored Procedure", cnBKTest)

cmdTest.CommandType = Data.CommandType.StoredProcedure

'Create Parameters
cmdTest.Parameters.Add(New SqlParameter("@UserName", Data.SqlDbType.VarChar, 10))
cmdTest.Parameters("@UserName").Value = userControl.UserName
cmdTest.Parameters.Add(New SqlParameter("@Password", Data.SqlDbType.VarChar, 10))
cmdTest.Parameters("@UserName").Value = userControl.Password

cnBKTest.Open()
cmdTest.ExecuteNonQuery()
cnBKTest.Close()

Is the procedure in the dotnetnuke database?

If so you could probably try this to grab it from the web.config file

Dim sConnStr As String =  ConfigurationManager.ConnectionStrings("data").ConnectionString

First of all, make sure your not modifying the core on a production environment. Second, you have to rebuild the solution. Then I would put a breakpoint in that code and run it in debug mode.

Note that modifying the core code is risky. It could really be a problem when you inevitably upgrade to a newer version of DNN.