Hi Mark,
I haven't tried it myself, but you may try the following:
1.
By taking a look at the instructions in the TechNet article you already mentioned:
http://technet.microsoft.com/en-us/library/dd282925.aspx , change the FormLogin.xml CONTROL
element type to be USER_ PROVIDED instead of USER_NAME, like this:
<CONTROL handling="real_value">
<TYPE>USER_NAME</TYPE>
<NAME>txtUserName</NAME>
<DEF_VALUE>USER_PROVIDED</DEF_VALUE>
</CONTROL>
2.
Then store the user’s UPN in the UAG SessionManager, still as per the instructions of the above TechNet article, as a Session Resource parameter, by
creating a [TrunkName][0 for HTTP or 1 for HTTPS]PostPostValidate.inc file in InternalSite\inc\CustomUpdate and using this line of ASP script:
SetSessionResourceParam g_cookie, "<Application ID>", “txtUserName”, "<User’s UPN>"
Note that you need to use the actual Application ID and the actual user’s UPN. Also note that the Session resource parameter name has to be identical to the <NAME> of the CONTROL as defined in FormLogin.xml, so in your case this seems to be
txtUserName.
Regards,
-Ran