[Serusers] Error checking

[sip]

I may have asked this last week, but if I did, I apologise. 

I have a rewriteuri call in SER.  It essentially forwards all the packets to a
different IP/port.  Sometimes, when calling, everything goes through.
Sometimes, that network is congested or confused, and I get a 404. 

I'm wondering if there's a good, clean way to handle those errors... is there
some sort of check status or some such I could use to handle errors from a
particular destination to which I forward certain calls? 


N.