How to show feedback messages in an editable data grid

I'm wondering if anyone has any advice on how best to display success/error messages when editing records in an inline data grid.

In my case, I've got an editable grid where records are saved (and validations are performed) as the cells are exited (or blurred). In the event of an error an error message should be displayed, and a "saved" message should be shown in the event of a successful save.

I'm looking for something subtle that informs without overwhelming users with feedback messages. Any advice would be greatly appreciated