Depends on where he died. Was it on the carpet? Get some carpet deodorizer and bring in a dustbuster. Use bleach spray on plastic & laminate surfaces. Febreze any cloth surfaces. No idea about wood. Oust works really well as an air freshener (I have two cats & two dogs).

I think nasty smells can trigger a psychological effect, so that you still "smell" it even after its gone. In that case, go cleanse your sense of smell by getting some fresh air. Get some coffee and inhale it deeply whenever you start to think about dead mice.

Sorry you have to deal with this.

Go to a place that has commercial cleaning supplies and tell them what you are dealing with. There are several types of enzyme based odor removers that are very good at breaking down organic residues.

Wasn't there just an AskMeFi about this last week? Worth checking out.

Call building management back and have them send maintenance to fix it. I'm serious, they should have done more than spray air freshner. My section does facilities management for a number of state-owned buildings and I cringe to think about the flurry of angry emails a dead mouse smell would bring.