Not that hard, if I understand you correctly. Here's a super-simple example, max 8 format. Uses a UDynaFlect deflector, which lets you choose arbitrary geometry. Replace the particle system and you're good to go. http://www.ericchadwick.com/examples/files/particles_filling_a_box.zip
I'm trying to get particles to stop moving after a certain frame. So for example a superspray would emit particles from frame 0 to 30, and then after frame 30 all the particles would stop moving, freeze in air, but still have everything else in the scene moving normally (cameras and such). I heard that this could be done…