Isn't it just a given inevitability that this will happen and as such trying to prevent it is putting an undue amount of effort into achieving nothing in particular?
The Dreaded "Pants Tent" Effect: Can Anything Be Done?? - Page 2
when you are standing the distance lets say is 12 lnches.
when you jack knife the trousers sitting that distance is now
only 6 inches. there is now a 6 inch surplus of cloth.
do this sit down and grab that excess cloth firmly .
continue holding the cloth and stand up. its a weird kind of fit?
but thats how we fit a person that is wheel chair bound.
low rise hip huggers would help and so would buttons.
But don't do this in front of said office-mates.
The solution to your problem is really quite simple.
Have your trousers made with 2 forward facing pleats, instead of reverse pleats.
Wear your trousers correctly. This means at the natural waist. The higher rise will get rid of the billowing.
Notice in the pictures where the waist is. IT IS HIGH.
That's one solution. Another might be for OP to make amends with his coworkers by sneaking up on them from behind and giving them shoulder massages. If OP is still self concious about his pant tent, he can hide it by snuggling in close to his coworkers. Who doesn't love a good shoulder massage at work from the creepy office guy a considerate coworker?