i dont really remember how its done in c-script but define an entity pointer array or use ent_for_name(or something like that).

ENTITY* doors[2];

and in the action use

doors[my.skill2] = me;

use difrent numbers for each door as skill2, and you may use the skill 3 to the target door(that needs to be closed if other one is opnened). like

if(doors[my.skill3].skill1 == 0) //iff the other door is opened(skill3 must have the other entite's skill2 value)

sorry for messing it up.