How to pass a multiselect parameter to a search?

I have a multiselect on session_id and created a search to generate session_id's for a particular user. I created a user text box and passed the `$user$` to the session_id multiselect where it populates that `$user$` session id. I want the option to select specific session_Id as well as select all. I set the default value to ALL as well defined `all=*`. When the search populates, it returns all users' session ID's instead of that particular user. Any thoughts?