The function will be evaluated dynamically when the property action has to be executed.
By default, the property action is executed when the security is loaded for the target object. But, you can change the event to trigger the action by clicking on the button "Select event..." when you create or change the property action.
In case of a property change, there are 2 possibilities:
1 - you trigger an event related to the VG Property Action
2 - An event is automatically triggers next to the property change, and you associate this event to the VG Property Action
Bottom line, when the property change happens, the event is triggered and the VG Property Action is executed (if the condition evaluating your function is successful).
Visual Guard .NET - Version 2.8.812.19