Check out Log.LockEvents
http://smartbear.com/support/viewarticle/14186/BTW, this is, in TC 8, defaulted to 20 to begin with (under Project | Properties | Playback) so, when there is a Warning and/or Error, the last 20 events will show up in your log. The idea is that this will give you some traceability to determine what led up to the Warning and/or Error.
If you have a lot of events showing up in your log, that probably means you're logging a lot of warnings and errors. Perhaps another tack to take is to determine what those warnings/errors represent and, perhaps, change that logging code so that you don't get quite so much "noise" in your log.