WCF Dialog Confirmation

Hi,
     I got a typical Situation. I got a
     1] Silverlight application,
     2] WCF Service
     3] .Net assembly which performs some action.
    
     From Silverlight application an operation is performed say Save which calls a WCFService which in turns calls a dll
     which performs some computation and waits for confirmation Now this is done on web do it is async.
     Now the problem is on replying Yes/No the operation has to be performed Is there a way to do it.
    

.Net Assembly This got some Message waiting confirmation

WCF Service

Sl Client After the message is displayed the client clicks Yes/No. On clicking YesOrNo the rest of the process done which is actually there in the .Net Assembly is this possible to do

     
     Hope i was clear, expecting a solution from you all guys.
      

Thanks & Warm Regards
Ganesh K