You can make doors that opens when triggered (for example with button, trigger_multiple etc)
And use trigger_changetarget to chamge target of this button/trigger...
It would look like this
**trigger (for example button)**(that is used to open dors)
target:blah blah blah (you can put game_text, or saound there, that says locked)
**another button(or trigger_multiple..)** (locks/unlocks doors)
target: door_changet (the name of trigger_chengetarget)
New target: doors
To make this process repeatable just make two multi_managers that changes target of lock/unlock button as well as open button...
Ouuu you can try to make multicource, it should work.. and it would be easier :D
Fuuu I thought one more way... you can make another doors in front of first doors...
So when you open doors that is in front of first ones (with button from somewhere) it would be awailable to go through...