If you have a copy of the Microchip Embedded Control Handbook, check out
the application note on page 3-121, "Software Implementation of
Asynchronous Serial I/O (AN555)".  This code is for a 16C84 using
an interrupt driven routine for RS-232 communication.  I've started typing
in the code for a project of my own.  If you like, I'll send it to you.
There are two disclaimers however, 1) It probably will not be debugged.
2) I'll need to figure out how to get it from my computer to my internet
host and then to you.

By the way, this routine sends the receive of the RS-232 to the RA4/RTCC
line of the PIC.  Therefore if the RTCC is set up as a counter loaded
with FF it will generate an overflow interrupt when the PIC receives a
start pulse.  The RTCC can be reconfigured as a timer after the start
pulse is received and generates interrupts based on the baud rate.