Usando flashvars
Al codigo de tu SWF agregale
<param name="FlashVars" value="ID=<% Request.QueryString("ID") %>"/>
debe verse algo asi:
Código:
<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="350" height="30" id="mi_flash_var" align="middle">
<param name="allowScriptAccess" value="sameDomain" />
<param name="FlashVars" value="ID=<% Request.QueryString("ID") %>" />
<param name="movie" value="mi_flash_var.swf" /><param name="quality" value="high" /><param name="bgcolor" value="#ffffff" />
<embed src="mi_flash_var.swf" FlashVars="ID=<% Request.QueryString("ID") %>" quality="high" bgcolor="#ffffff" width="350" height="30" name="mi_flash_var" align="middle" allowScriptAccess="sameDomain" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer" />
</object>
Fijate q se pone 2 veces ojala te sirva