Hicks-law choice RT task

[I][edited from support email][/I]
I'm conducting a Hicks-law choice RT task. The goal is to establish a response-tempo using a series of tones and visual stimuli prior to the appearance of the target stimulus. Think of it as a count-down. For example, 5 tones are spaced 300ms apart, the target is displayed, and after 300 ms, a response tone should be played, specifying to respond "now". It's no problem getting the pre-target tone sequence going, but I want to start timing the RT from when the target 1st appears, and I want a tone to play 300ms after the target appears, while it is still on the screen. In other words I need the option of recording anticipatory response times. Unfortunately, once the rt: syntax is specified as the time, the target displays until the trial times out, and only then does the tone play, after the specified 300ms delay.
I tried displaying the target, and using the clear screen option with the rt: syntax, and redisplaying the target, and playing the tone, but the clear function operated very slowly, and leaves a noticeable blank screen gap. And if I use the the 0,0,0 loc parameter for the new stimulus and final tone, the stimulus does not reappear until after the 300ms tone delay expired, then the target and tone are displayed at the same time.
Any ideas for a work-around? Is there a functional syntax I'm missing?

It's always tricky working out a way to execute a stimulus presentation [I]while[/I] an RT is still being taken. In the case you are describing, you might try the following.

First, create a new version of that subsequent sound--one that has 300ms of quiet at the start of the sound file. Then, play that file immediately *before* the target with a [I]time[/I] value of [I]0[/I]. That will cause the sound file and the subsequent target to execute simultaneously, but the RT will be taken to the target. Meanwhile, the sound will continue playing and you would thus hear the tone at 300ms into the RT. Do you think that would work for you?

-Blair