You need to use an evaluation software program such as WinCycle, MultiCycle or ModFit. If you have a good control/calibration sample, with the help of software you will be able to make a good analysis. You need have a reference to make a successful evaluation. I suggest you read DNA Measurement and Cell Cycle Analysis by Flow Cytometry by Raphael Nunez in Curr. Issues Mol. Biol. (2001) 3(3): 67-70 before you decide on the software to use. Best wishes,