ALv events

In an alv grid, one of the column is having a drop-down list, whenever i select a value in the drop down list , based upon this new value another column value should be changed, it is changing but it is happening only after pressing the enter in the newly selected cell value of drop down. I want to change it as soon as i select the new value from the drop down list but not after pressing enter key. For this i am using data_changed event of the class cl_gui_alv_grid.