Our Intranet has a page where users can update their own details using AD Self Service. I want to add the field ASSISTANT to the page. This is fine except that, as I cannot add this as a general attribute, it must be added as a custom attribute. This means I cannot get it to do a lookup for a valid entry for this field. (I need it to function somewhat like the MANAGER field)

Can someone advise how I can get a custom attribute to do a lookup, or how I can add ASSISTANT as a general attribute?