REFRESH ALV Grid on Refresh.

hi guys,

can neone tell me that how to modify a internal table which is passed to a ALV GRID output....i have added a refresh button on the grid.now my grid has to be refreshed when i press the refresh button ..n whatsoever changes has been made in the main table from where i am getting the data in my internal table that changes has to be seen in my grid.

have heard of some parameter in alv grid display function module which refreshes the internal table.