I need to pass some variables from the DNN database namely a custom field in the user database that I have created and populated.

the offsite URL/App will accept this for entry: https://offsiteapp.com/login.aspx?customid=12345 

I'm familiar with passing form fields (hidden or not)  using HTML. (i.e. <form action="anotherpage.htm">)

But I'm not sure how I would pull this off in DNN or if it's possible at all.

Thanks

-jb

Ideally it would be in an Iframe. because I would like the "transaction" to take place transparently to the user.

I have the backend built already that has usrs documentation, forum etc. that they access usng their owner number and password (using DNN's database). However their financial data is not held in DNN, rather it's accessible from a third party app on another domain. The other app is all set up and ready to accept a custom ID  (as above). I have already made a new field in the database"customid" and just need to be able to pass that value on to the other page.

If I put this in an IFRAME and craft the asp page like so:

<% Dim sConn As String = "Data Source=mydatasource;Initial Catalog=db;UserId=db_user;Password=password;" '
        Dim oConn As New SqlClient.SqlConnection
        Dim oCmd As New SqlClient.SqlCommand
        Dim oReader As SqlClient.SqlDataReader

        oConn.ConnectionString = sConn
        oConn.Open()
        oCmd.Connection = oConn
        oCmd.CommandText = "SELECT customid FROM Users WHERE UserID = ???????"  `this is where i lose it.
        oCmd.Parameters.AddWithValue("customid", UserID) 
        Response.Redirect("https://offsiteapp.com/login.aspx?customid=" & oCmd.ExecuteScalar)
        oConn.Close()
%>

it's like halfway there... but I can't rap my skull around the other half. I mean thats how I post it to the next page but it'll break at "WHERE UserID=" because the page has no way of knowing what the current userID is.
I'm assuming a coded IFRAME put in a Text/HTML module wouldn't be able to tell either? or can I use Token Replace as long as the code is sitting in a T/H module. 

honestly I'm just confused at this point.