How to go about fetching offsets for locks?

[temnix]

I'm interested in going through every locked chest and door in every area, whether there are few or many in a given place, or none, and putting an item in the KEY field, for a universal opener. How do I do that? Every area is goint to have different offsets, and they may (I don't know) change with alterations to the area brought by mods and what not. Is there some way to go through Door1 if-it-exists, Container 1 if-it-exists and so on automatically?