如何在Web服务上进行呼叫后处理？

Is there a way to have a web service (WCF/ASMX/etc) call do some processing after it returns it's results? Note I'm not looking for a asynchronous calls as the client needs the result back ASAP, before the the extra processing is done.Is there a way to have a web service (WCF/ASMX/