IIS Basic Authentication as LDAP login?

We have SuiteCRM 7.3.1 installed on IIS 8 with Basic Authentication set. In SuiteCRM we have LDAP authentication enabled.
Does anyone know how to pass the IIS login info to SuiteCRM so users do not have to log in twice?
I’ve searched the code but can’t figure out where the variables are being set or what function to fire for the login.

Figured it out by altering the login.php script and adding some javascript to the login.tpl