Coding CPU Usage (%) Column similiar to WIndows Task Manager

Hi I have been trying to code something similiar to the Windows Task Manager, but for multiple PC's. I have been able to get most columns I need except for the CPU Usage column (the % of CPU for each process). It is fairly easy to get the total CPU Usage for the machine but for each process is not as easily documented. I have looked on the net and see other people are trying to do the same thing. I am totally stuck with this. Any help would be most appreciated