Thanks Darrel, so to be clear in my mind, I would do this:
poll pir1.5 in the main loop
If set, jump to serial routine

serial routine:
check time to talk flag
If set, HSEROUT an ack and then HSERIN waiting for whatever
Else HSEROUT no time
return

Now how did I get the info in the buffer? Does HSERIN grab whats in the buffer, or look for new received bytes?