tlantz-
for high time accuracy, i would use some "analog output waveform" vi where you seed it with a square wave, then set the buffer to "repeat". check the "AO Config.vi" and the help files.
if you don't need such great time resolution, you can just use a while loop and a timer and switch the output values using "AO Write.vi" or something like that. but this will probably only be accurate to around a few milliseconds or so if you have your loop running full blast. the advantage of this method is that it is simpler if you have less experience with analog output stuff. some methods of timing the loop will be much more stable than others.
anyways, one of these two methods should work. check the example vi's also, i'm sure there are ones similar to
what you are looking for.
micah
