Bernhard,
There are no utilities in IMAQ to save image sequences in a single file.
One possible solution, if you aren't trying to compress the images, is to extract the 2D array of pixel intensities and save them as a standard array. You would be able to store as many arrays as you want in a single file.
If you want to compress the images, there are utilities for creating AVI files. I have used a wavelet compression utility that I wrote LV drivers for, also. If you are willing to spend a little money, that might be a good solution. You can contact me at bruce@ammonsengineering if you want to discuss it further.
Bruce
Bruce Ammons
Ammons Engineering