recording RT with delayed stim presentation

Hi.

I need to modify a go/nogo task (which I already have) and I am having some trouble. In the task, I will be presenting stimuli to which the participants respond (or not). This I can already do. Now, I need to present a sound file (with a TTL) 300 ms after the presentation of the go/nogo stimulus. How can I (a) present the sound file after this 300 second delay while (b) recording the RT for the previously presented go/nogo stimulus? I suppose I could introduce a blank stimulus for 300 ms after the go/nogo stimulus and then present the sound, but how will I allow participants to respond to the go/nogo stim, and how can I record the RT of this response from stimulus onset?

Thanks!

The sound file could be done by inserting 300ms of silence at the start of the sound clip (in a sound editor like [I]Audacity[/I]) and then playing it [I]before[/I] the main stimulus but with a [I]Time[/I] value of 0ms so that it (i.e., the 300ms of silence) starts in synch with the main stim.

As far as I know you can not send a TTL out in the same way. Once you start recording the RT you can't start another event like that. The only way I could see doing that is to do the sound as described above and send a TTL signal along with it at onset (before the main stim) and give it a 300ms duration. So you wouldn't get the signal at 300ms, but you would get the END of the signal at 300ms. Would that help as a marker?