so you want to be able to recruit 'a unit' which is tied to a hidden_resource, but only after a specific building has been built?
Meaning, the hidden resource alone is not enough to recruit this unit?
if thats the case, in the EDU wherever you see this unit in question it will have somthing like this...
Code:
recruit_pool "Mongol Horse Archers" 1 0.25 2 0 requires factions { mongols, } and hidden_resource Mongol_Heavy_Archers
simply add somthing like this...
Code:
recruit_pool "Mongol Horse Archers" 1 0.25 2 0 requires factions { mongols, } and hidden_resource Mongol_Heavy_Archers and building_present_min_level 'building of your choice here'
Somthing like that might be sufficient for what you're looking for?...