Sending a variable without it being seen

Hi. Is there any way variables can be sent without them being seen? I am trying to set a session variable from data that is pulled from MySql. I have 2 frames open , the first frame has the options available which when selected sends the variable info and opens a page in the second frame. This page then registers the variable showing the selection. I am currently sending the info like "pagename.php?variable=what target=frame" The links are generated from info in MySql and therefore I have not managed to send the info in a form using hidden fields. The main reason for this is security. Users should not know what variables are being passed or needed. Thanks Kevin