How to add two buttons in ajax modelpopup in wordpress?

I have been searching myself silly for this and can't find anything to help. I want to add 2 buttons to my nav_menu one for register and one for login. also i want it to popup with the ajax and can't seem to find that either. I don't want to use the pages for registration or login. Can somebody help me on this.

Thank You

via Chebli Mohamed