Giulia, yes, that is exactly what we mean. The way to implement this depends on what version of LabVIEW you are working with. If you are working on LV 7, then there is a good library of functions called Signal Manipulation that would allow you to easily handle and work with your data once they have been acquired. Basically you should go through your scans and check when the trigger has come in. Depending on the position of the transition (from 0 to 5 V I guess) you can roll back N samples and save those N + M samples you are interested in (being N the number of pretrigger samples and M the number of posttrigger samples).
I think it would be best if you call directly by phone one of our Engineers at NI Italy and discuss the problem directly with us. AlessioD National Instruments
