Public Event MouseLeftButtonUp As MouseButtonEventHandler

Dim instance As ISPanel
Dim handler As MouseButtonEventHandler
 
AddHandler instance.MouseLeftButtonUp, handler

public event MouseButtonEventHandler MouseLeftButtonUp

public event MouseLeftButtonUp: MouseButtonEventHandler; 

In JScript, you can handle the events defined by another class, but you cannot define your own.

public: __event MouseButtonEventHandler* MouseLeftButtonUp

public:
event MouseButtonEventHandler^ MouseLeftButtonUp