Call back methods for events and cell controls are designed to be used for different circumstances. Here is a brief example of when these call back methods execute.
The call back method installed to trap the On Clicked event using PV ON EVENT will not run if the user clicks on a cell that has a control set (e.g. a Pop-up menu). Mouse clicks on a pop-up menu control cause the execution of the call back method installed for that control using PV SET CELL CONTROL.