pass variable to dynamically populated drop down

[tribak]

We have an online application html form that pulls the open positions into a menu/list select field from an xml file. You can see the form here: enter link description hereFor each open position there is a job posting page with an apply now button which links to the application page. We'd like to pass the position to the menu/list select field in the form when a user hits the apply now button. So If I make a form on the job posting page, and use a hidden field to hold the position from that page, then how do I pass that variable to the online application to select the position.