Federation : TARGET value as the RelayState=value

I have a Siteminder protected application that calls a Federation login process.  After it completes the Federation process it needs to end up on the page originally requested. In Federation it hits the redirect.jsp and is then forwarded to the Login.fcc.  I need to get the “”TARGET” value from the URL POST  and append the TARGET value as the RelayState=value to the POST to the login.fcc POST.

I can get the TARGET value with JavaScript in the login.fcc.   How do I append the RelayState=value to the POST within the login.fcc?

POST https://server.foo.com/affwebservices/ldap/redirect.jsp?SPID=myapp&TARGET=$SM$https://server2.foo2.com

POST https://server.foo.com/affwebservices/ldap/login.fcc?SPID=myapp&RealyState=https://server2.foo2.com&TARGET=$SM$https://server2.foo2.com

Thanks