if its supposed to be triggered as an event: if there is a python function (or better yet an xml tag) that returns which milestone is currently achieved, its easy to trigger it:
create a trigger for each milestone that is supposed to trigger a GA, set it to active 100%, iweight -1, non recurring, non global and it will trigger immediately upon reaching the milestone and only once per player (team? <- not sure).
create a trigger for each milestone that is supposed to trigger a GA, set it to active 100%, iweight -1, non recurring, non global and it will trigger immediately upon reaching the milestone and only once per player (team? <- not sure).