I would like to emulate the auto-fill / drag-fill functionality in Excel, i.e. when you select one or more cells in a row then a border appears around them, with a small cross in its bottom-right corner. Dragging this cross down over subsequent rows results in the values in the selected cells being copied into the cells of those rows.
I suspect this is asking too much of the DataGrid, but would be interested to hear ideas as to how it may be achieved...