I am pretty sure the Trip freeze is only done by scheduling for a whole bunch of reasons. There are many awarded trips with pending hotel/transpo and that is not the reason for a trip being frozen then unfrozen. Unfreezing of a trip may be as simple as every required department acknowledging within the company that the trip exists and they are working on it. Once the trip is unfrozen, then the trip is processed for trading. I haven't used the make-up section in a long time, but when I used it, all I received was a crew notification that my make- up request was approved and then I found out what I was actually going to fly. I have also had a scheduler call me to see if I wanted to accept a trip that was close to what I entered, but one of the filters stopped it. So that is why I am thinking that schedulers may look at the make-up requests before they start hitting enter to process the normal trip trades. Again, its been over 2 years since I have used the general make-up, but I am going to start using it.