Collecting RTs during animation

Hi everyone,
Does anyone have know a trick for collecting keypress reaction times
during smoothly moving stimuli (using OpenGL PTB)? The fastest CRT I
have access to has a 100Hz refresh rate. If I can only call KbCheck
once per refresh, I'm limited to checking every 10ms, which is
probably not good enough. Has anyone devised a method that gives
better precision? I thought about launching a seperate thread, but it
appears that Matlab doesn't support multiple threads.
Thanks for any advice,
Tim Vickery