Hi Phani,
True, with a TimedTrigger you would need to guesstimage the amount of time. Here is another idea-- I'm not sure this will work with the sequence of events in the phase model, but maybe worth a try.
In the handler method of the display button, instead of getting the ALV data, instead fire three events...
- show_loading_image
- get_data
- hide_loading_image
In the event handler method of each event, do what the name suggests. In event show_loading_image, just make the loading image visible. In event get_data do your updates to the ALV data. In event hide_loading_image, hide the loading image.
It might be easier to upgrade. 
Cheers,
Amy