Ok, so your example worked. And I created another template (macro enabled) and that worked too. However the template I've added it to is the 'normal.dotm' template and that is where I am having problems - I probably should have mentioned this at the start but thought it was the same as other templates.

I've taken a copy of the normal.dotm and renamed it to notnormal.dotm and documents created from that template have the Custom Document Property, if I rename it back to normal.dotm documents created from it no longer have the CDP.

Seems to be the case:
http://windowssecrets.com/forums/sho...-field-to-Word

http://www.vbaexpress.com/forum/showthread.php?t=5119