Passing a session_variable through master-detail pages

I am using a DW8 Master_Detail server behavior and pages from which I would like to generate an email from a customer to an admin location. As part of that process I would like to carry the customer's email address from the Master page over to the Detail page so that the form there can have that information automatically filled in. I then would like to use the information on the Detal page sent via email , rather than Update or Modify the record itself. The customer's email address is not part of the particular recordset, nor should it be.
Having said all that, my plight is that I have not been able to bring over the session variable 'MM_Username from the Master page to the Detail page. I am able to pass it to the Master page from the customer login screen. Trying to send it as a URL variable from the Master page to the Detail page did not work either. No luck.

I know the technique must be simple but so far all techniques I have tried have bombed . . .

One of the issues is that I can't see how DW is posting the data from the Master page recordset to the Detail page when I look through the code view. Any clarification or assistance would be greatly appreciated.
Thanks, Dale 🙂