delayed_callback
This event is triggered if the user changes the selection of cells. The ALV Grid Control triggers this event with a short delay of 1,5 seconds.

You are strongly recommended to read Using the ALV Grid Control in WANs before using this event.

The ALV Grid Control triggers this event only when the cell selection is changed interactively by the user. The event is not triggered by methods like set_selected_cells etc.
For an overview, see: Events of Class CL_GUI_ALV_GRID