Well.. if you've tried having him to go all the positions in that building.. it could be that they just didn't make one for that spot?
I know from making a couple of buildings that it is a very specific point that must lay along a path the AI will follow through the building.. so maybe that point you're trying for is really just close to the balcony..
If that's the case you could try setpositioning a small object just under where you want the unit to stand and use:
unit domove getpos object
to try and make him walk over to that spot himself....
all sounds good in theory.. ;D