Help with script

Hi,

I'm just trying to create a script which automatically:

> Checks the selected layer is a target (or 2 node) camera

if yes then

>Creates a new 3d Null object [name = same as selected camera plus '_Target']

>Links the position of the selected camera's Point of Interest to the position of the new Null object

If anyone could help me to piece this together I would be very grateful.

Thanks

Spencer