In VLF-ONE the system IIP (Imbedded Interface Point) provide two methods that you can overload to perform special logic whenever the main window (the web browser page) is opened or closed.

These are called:

Refer to Imbedded Interface Points (IIPs) and the shipped version of reusable part UF_OSYSTM for more information about these methods and about how to implement you own IIPs.