i've never tried this, so there are just some ideas
1. change the door to a func_wall, then change it back or set the "speed" to 0
2. i know that setting a player to SOLID_NOT allows other players to walk through them, it would probably have the same effect on a regular ent. If not set the absmax and absmin to 0 (or the mins or maxs), i think one of them determines the actual part the player hits.