You can read more about the process here. To simply the process, an HTML file was created that uses JavaScript to generate the URL based on the following information
Download HTML file at CodePlex https://adfsrelaystate.codeplex.com/releases/view/93202 AD FS 2.0 Rollup 2 http://support.microsoft.com/kb/2681584 Supporting Identity Provider Initiated RelayState http://technet.microsoft.com/en-us/library/jj127245(WS.10).aspx