Ok if I understand what you are describing, the simple solution is to capture the time with the spacebar, double click on the result time to edit it however is needed and enter the correct bib number then save. Here is where I am confused and won't be able to test this until later, when you do this, it should automatically assign that time to the correct race because the participant(bib#) is assigned to the event and the software shouldn't be automatically switching events. Regardless, lets say it doesn't put them in the correct event. right click on the participant in the athletes tab and switch them to the correct event. If the start times are different, you will get a pop up asking if you want to correct the time. Click ok and the participant will be in the correct event with the correct start time and a finish time corresponding to the timestamp you captured with the space bar.
Or did I misunderstand the question?
I can't verify this right now but I believe the "clock time" that gets captured is whatever event is the top clock, nothing to do with the public display but I may be mistaken. I thought you use to be able to select events after you had started them, you could actually select which race you wanted to capture times for, I don't know what happened to check boxes on the clocks after you start them.
If it is found that capturing a time and adding a bib number to it can in fact switch someones event or add them to a differnt event, that is something brian might want to look into.