Basically, DirectRT will record the reaction times in the output files for any keypresses defined in the input files; there is no way to selectively determine whether a defined keypress is recorded to the input files or not.
You can control which keypress is the TRUE respsonse by listing it as the first valid response for that stimuli. In your case, that would mean that pressing the space bar for the first stimulus requiring a keypress would be labeled as TRUE in the output file while any of the function keys would be labeled as FALSE in the output file. For the second stimulus, the keypresses on the numberpad would be labeled as FALSE because they are not the first keypress defined. You will find all of this information in the log file for each participant, as the short output file only displays the data for the last keypress defined in a row of the input file involving multiple keypresses.
Jason Reed
Empirisoft Software Support Specialist