Diplo,
Unfortunately, there is no way to fire the AcquiredData event before NScans are acquired. You may want to consider performing your acquisition without events. You could use either the AcquireData or Read method. The AcquireData method is used in the following example program:
C:\Program Files\National Instruments\MeasurementStudio\VB\Samples\DAQ\Analog Input\Acquire N Scans without Events
Good luck with your application.
Spencer S.