I have added a Custom property called "division" to the User Profile
Properties.

To do this I followed this path:

Shared Services Administration: Intranet SSP > User Profile and
Properties > View Profile Properties > User Profile Property

I wish to map this attribute to AD.
In the Edit User Profile Property page the Property Import Mapping
area the option is not available.
I have the only the Source Data Connection field showing the Master
Connection.
I'm sure that this is a simple switch that I have not enabled.