[Serusers] lcr module question - how to implement nice routing logic?

Hi, Is it possible to use lcr module so that when the routing logic checks it won't change the request URI but only change the destination of the SIP message?? I would like to utilize this module to select if the outgoing message should be forwarded to boundary SIP Proxy or to SIP/PSTN Gateway. Could You Please give me some clues or point another way to do this? Thank You for any help. Cheers TOmasz