Sending a request to a url but not returning the page to the user

Hi,
Still trying to figure a couple things:)

Actually I need to call a direct action of application B from  
application A, but I don't want the user of application A to "see"  
this request. In fact the action he triggers return something for  
him, but I need a "second" action to take place.

More precisely I need to call a direct action on my front office  
application when an administrative user save something in the back  
office application to invalidate the front office shared editing  
context.

I think I already saw something like this on the mailing list but I  
just can't find it:(

Thanks

Xavier