(QUESTION) how to mask elements without depth and scissors

[lascdre]

i need to make scrollable dropdown box, but for this i need to mask elements and i cant use depth mask because im using glTranslate Z so that dropdown box is on top of all elements (other group boxes) otherwise it will be behind him (who dont knows if you use glTranslate after u used mask translating will not work), i cant use scissors because i already using it for scrollable group boxes list

what should i do for mask elements? (except depth mask and scissors)
p.s. sry for my bad english

 

[lascdre]

no need anymore, released that through scrollindex and get values from dropdown list by index