Office Communicator 2007 send message from javascript

Question

I'm trying to open an OC chat via a link. Currently working with code like this:

window.open("sip:[email protected]"); 

But I would like a custom message, the same way it works with emails

window.location  = "mailto:[email protected]?Subject=subject&body=body";

So it may look like this:

window.open("sip:[email protected]?message=messageText"); 

Is it possible?