I have done some experimentation with applications that creat lots of objects. I have developed some ideas that may be helpful, which I will offer below. This seems theoretically very difficult to do. The GC runs independent of the routines. So it may consume time during a routine, while cleaning up objects created by another routine.
Garbage collection is a global function.
So I recommend that instead of looking to the profiler for information, you measure the impact on a global basis. The difference suggests approximately how much of a burden GC is on your application. If they are similar, then GC is not a bottleneck. If they are widely different, than GC is a factor. I have found that the current ISE GC is pretty good in most cases.