Thanks for your help.

However if I replace this line :

Code:
 mygrid.getView().updateLiveRows(grid.getView().lastRowIndex,true,true);
with this line :

Code:
 mygrid.getStore().load();
The data is well refreshed however the vertical scroll is also reset I start reading the datagrid from the beginning. (It is the same action as the refresh button in the bottom toolbar).

Is there a better way to refresh only the current visible part of the grid?

The final idea is to use highlight color for each updated rows like this:

Code:
 var row = grid.getView().getRow(rowIndex);
        if(row!=null) {
          var el = Ext.fly(row); 
          el.highlight(color,{"duration":3.00});
        }
Thanks.