Is there a way to get the username from the Windows Authentication Scheme?

Hello members,

         I have a specific need on an integration that we have. We have a custom authentication scheme where we leverage the HTML Form(username/password) and in the custom auth scheme we get the username to redirect to our integration and everything works just fine. 

         I now have an urgent need to not use HTML Form and instead use Windows Authentication for 1st factor authentication. Our custom authentication scheme is expecting a username in order to pass it to 2nd factor authentication. So I need to find out if it is possible to get the username from a Windows Authentication Scheme somehow in SiteMinder so I can pass it to my custom authentication scheme.

Thanks in advance.