Gelatin to keg

Is it too late to add Gelatin to the keg once the beer has been transferred and the keg pressurized?  It would mean opening up the keg to put the gelatin solution in and therefore exposing the beer?

I almost always add gelatin solution to the keg just before pressurizing, but have forgotten a few times and added it up to 2 or 3 days later with no adverse affects to the beer. Being careful not to splash or agitate minimizes the amount of O2 introduced, most of which will be forced out by gently purging several times.

I will be adding tonight so its only being pressurized one day, so hopefully will be ok

That's fine, it'll take a bit more time for the coagulation to drop.

Mark