From tech support:
How do I process a random sampling of events form my file/gate?
There is a way to randomize, but only in version 8 of the software. It involves exporting a certain number of events - either from the top-level node (ungated file) or one of it's subpopulations (gates). You can select files/gates one at a time, click Workspace menu, Export. There, you'll see a number field with current event count. You can modify it, and the sampling will be "random" according to our docs, but I don't know which random algorithm is used.