I am not aware of any callback mechanism that lets you know when the grid has started loading from the underlying data source and when it has completed.  You would definitely need to do something with threading so as to not block the main thread, but I'm open to input from other people on what you might listen to that for sure know that the grid is done loading all the rows.  You *might* be able to hook the InitializeRow event and check to make sure that all rows have been initialized (i.e. you've found a row whose index = datasource.Count -1), but I'm not sure that this will for sure fire when you'd expect it to.

-Matt