asterisk users - May 2008 - Passing Dial URL argument through Asterisk

Hi,

I'm able to send an HTML Frame to an IAX2 phone like Zoiper, Using 
Dial(IAX2/...,,,"http://site/uri")
but now i need to do this

    Inbound Call == Zap ==> Asterisk-1 [main diaplan, build the needed 
Url ] == IAX2 ==> Asterisk/2 == IAX2 ==> Phone

By using a tcp trace i can see that the HTML frame is send to Asterisk/2 
but there is no ${URL} variable set
and so i don't know how to transfer it to the queue and then to the phone.

Any idea ?
Did asterisk even parse the inbound HTML frame ? i can't find evidence 
of this in the source code (rapid glance).

Regards,