Silverlight DataGrid not returning to edit mode after child window popup

Question

Basically what I'm doing is using the EditEnding event on the DataGrid to check for certain errors and then if found use e.Cancel and a child window to display the errors. Now if you just use e.Cancel without the child window the focus stays on the cell and you are able to edit, if after the child window though your focus is still on the cell but your not in edit mode.

Any ideas how I can force edit mode back onto the cell after the child window?