Assuming that I have two IChangeSet objects that are from the same history of a component in a stream, what is the best way to get all other changesets between them in the history?

For now, I'm doing the (extremely) suboptimal solution of getting all of the ordered changesets on a stream and then searching for the start and finish and just pulling all changesets between them.

There must be a better way to do this - over time, this will get to be ridiculously expensive and huge in space. I know it must be possible, because the RTC Eclipse GUI allows you to select two changesets in a component's history and then displays everything that happened between them - I just can't find where it's done.