I'm not entirely sure you can,
Are you wanting these variables to be passed when the user clicks on a link ??
You could use a form with hidden variables, then use a javascript onClick="window.forms[0].submit()" event. ie
<a href="javascript:window.forms[0].submit()">Submit</a>
or if the flash page is in a different window / frame, you can do it in an onLoad event ie.
<body onLoad="window.forms[0].submit()">
and set the form tag to have a target of the frame / window ie.
<form action="flash.page" target="targetname">
...