Notification

Question

Hello All, I don't sure whether the subject reflect what i'm going to ask, and i'm sorry for that. How to know (by code) when an application is loading? What i want to do is : if i open up MS word, my application will run. It's kind of rental system. As long as i use MS word, the application will continue record the time i use in using MS word. After i close MS word, the application will calculate the cost i must pay based on time i use with MS word.