You should be able to handle this application from Signal Express and LabVIEW. In Signal Express you will add a Digital Output step. See Figure 1. You are getting that an "external clock" is required because you are probably already using your clock on another task. You may post your Signal Express project if you want.
For logging the data the pulse I will kind of prefer using LabVIEW, especially example named: “Write Dig Chan.vi” where you can software timed your pulse and log the time when it was sent. What I ould suggest is to get the hardware part working first and then if you need help on how to log when the pulse is sent post your question in a LabVIEW forum.
I hope it helps
I have been playing around with Signal Express and it seems to me you won’t be able to take the signal back to low when you stop the record automatically. You can still manually changed yourself. I guess you have a record that starts and stop automatically and when it does the line stays high. If this is the case you I don’t think you can automatically drive the line to low since this card is software timed, Signal Express controls the state of the line and you have to manually change it.
This might be a job for LabVIEW. Did you have the chance to take a look at the example I pointed you?
Waiting for you reply