Research options

[Gistergingol]

Hi, i have a problem, i have a building that has many researchs available, but i don't want to show them all to the owner of the building, for example RESEARCH1 is showed, RESEARCH2 (can only be searched if you've searched RESEARCH1), RESEARCH3 (can only be searched if you've searched RESEARCH2) and so on... Is it possible to show in the building only researchs that can be studied at the moment?

Oh by the way i know i could solve this problem using Improvement instead of Research function, but i based ALL triggers (more than 40) with research function, so i should make all triggers again..