Hi all! Back from holiday!
I don't believe you can add opening doors to an object, you would need to create the object yourself with Gmax - Create your hangar in Gmax with the door animations as you want them and export with MDLcommander installed to enable you to select "keep files". You can then use Arnos (scenerydesign.org) super CAT (conditional animation tool) to edit the YourObject_1.asm file and add the frequency as a condition.
This wont mean much if you don't know much about Gmax! But thats a different question

Lol!
Hope this helps!
Birdy