Dynamic update statement in INSTEAD OF UPDATE trigger

It is possible to use dynamic base table update statement in INSTEAD OF UPDATE trigger. I have a wide table (more then 100 columns) and so I don't know, how to forward updates to only really updated columns of base table. Dynamic SQL in trigger cannot access to inserted table. Copying inserted to #inserted then building dynamic update statement based on columns_updated() function leads trigger recursion, not direct base table updating. Update statement in INSTEAD TRIGGER cannot vary updated columns list. Is there any workaround?