Help To Install External Pir To Honeywell Dvr Via 15 Pin Com Port

I have a Honeywell DVR HRTL-One with 80gig hard drive. I want to use this so that I can record only when motion is detected.

The DVR does not have motion detection s/w built in but does come with a BNC in/out and a 15 pin COM Port pin out as described below:

pin 1 - external device control

pin 2 - external device control

pin 3 - Video loss

pin 4 - Switch out

pin 5 - error out

pin 6 - Rec start

pin 7 - external alarm NC

pin 8 - external alarm NO

pin 9 - GND

pin 10 - RS-485B

pin 11 - RS 485A

pin 12 - disk full

pin 13 - alarm reset

pin 14 - Alarm input

pin 15 - COM

I already have a camera which continuously records (via BNC in) but need to improve on this so that it only records when motion is detected in the driveway outside.

Can anybody advise on an external PIR sensor to install and which outputs from this PIR go into which pins of this 15 pin com port that looks like a serial port.

Alternatively, could I replace my camera with a camera with built in PIR and connect to the BNC input - this way, the DVR would continously record until there was video loss (ie. no movement).

Any advise would be greatly welcome.