Chase triggers are lame, so I don't advocate them. However, you could set different attack alias buttons for manual chasing in your numpad. Target flees north and you can then press 8 and 7 for north and trip @target. Setting up the cool ++ alias system where ++ replaces your target would be particularly useful for the future ease of setting targetting commands in your numpad (otherwise you would have to make an alias for each command).