Loading Only Part of a File

I have a file with about 50million data points, but a lot of that is excess data. Instead of clogging up the space in Igor, I was hoping to be able to only load part of the wave. I need to pick a specific part of the wave to load. I know how to do this for an image, but I am wondering if it is possible for a data file. If anyone knows how to do this I would greatly appreciate the help.
Thank you in advance.
Look a the LoadWave operation /L flag.

If that does not do the trick then I need specifics on the format of the file.