Description Philipp Hahn 2013-06-20 12:12:22 CEST

'_view_computer': univention.admin.property(
....
                        syntax=univention.admin.syntax.XXXXX,
                        multivalue=True,
			may_change=False,
			editable=False,
			),

class XXXXX(UDM_Objects):
	udm_modules = ("computers/computer",)
	udm_filter = '(&(objectClass=xxxxxReference)(xxxxxNumber=*))'
	regex = None
	key = 'dn'
	label = "%(fqdn)s"
	simple = True
	empty_value = True

In UMC-UDM the ComboBox field is grayed out, but + and - buttons next to it are still clickable and do add/remove additional entries if at least one entry is set (that is a referenced entry is found in the scenario above).
If the value is empty (no referenced object found), the + button is already initially disabled.