Nitrof,
You could use the All VIs In Memory application property and do a compare every few seconds to see if a New VI has been opened.
Do you need to know when a new VI is run in an application or when a new VI is created new and design is begun. If it is the first, use the first answer posted. If it is the second, use the method that I have suggested.
Randy Hoskin
Applications Engineer
National Instruments
http://www.ni.com/ask