Making a lever unlock a door?

[Wyz]

Thanks for answering my last question, but a new one has arisen. In my cs, I have a .map called 'The Undercroft', where you need to go down a few levels and pull a lever. This lever, I pictured, would open a door back up on the main floor that was previously locked for security reasons. How should I go about this? Should I make a GetLeverState function of sorts that will set a global variable to true, unlock the door in a different map? The separation of maps is the tricky part Thanks