Technical DIY intrusion alarm

[PeterM]

I wish to make up an intrusion alarm that is activated when the doors are locked via the remote for my Ducato 2006 2.8JTD. I have read some of the older threads about fitting an alarm but they are not helpful enough.

Any advice about which wires in the door to tap into? I am attaching a wiring diagram and functional description for a 2003(?) JTD that should be close enough.

Any experience doing similar?

PeterM