XBee to replace serial cable

Hi,
I've got a question I can't find an answer to...
I have a device which is controlled by a PDA via a null-modem cable. I want to replace the cable by using 2 xbees in transparent mode. The problem is, the device uses RX, TX, CTS and DTR pins to talk to the PDA. Apparently, XBees do not have any control over DTR pin (they can read it, but can not set it). Plus, the Xbee on PDA side should control this pin in sync somehow.
Do you think it's possible to solve anyhow? I was thinking about having 2 arduinos reading serial port pins somehow, and wrapping this info and sending it via Xbees in API mode together with data, but it might be too slow...
Please, I need ideas!

P.S.: I'm using XBees PRO 900MHz HP with serial explorer boards.