How to get a variable from the object tag

programming flash
1

I need to get a variable from a param in the object into flash and apply it to the onclick event for a button. Can anyone help me out with that? Snippet below

<object classid="clsid:d27cdb6e-ae6d-11cf-96b8-444553540000" codebase="http://fpdownload.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=8,0,0,0" width="320" height="240" id="source" align="middle">
 <param name="allowScriptAccess" value="sameDomain" />
 <param name="flashVars" value="urlToGoTo=http://myurl.com" />
 <param name="movie" value="http://myurl.com/Controls.swf" />
 <param name="quality" value="high" />
 <param name="bgcolor" value="#ffffff" />
 <embed src="http://myurl.com/Controls.swf" flashVars="urlToGoTo=http://myurl.com/" quality="high" bgcolor="#ffffff" width="320" height="240" name="source" align="middle" allowScriptAccess="sameDomain" type="application/x-shockwave-flash"/>
</object>

This is the variable I have to capture and apply to a button.
urlToGoTo

As always thank for any help.