How to retrieve the Cell or Row value for Silverlight DataGrid, when using ValidationSummary

Question

I'm adding items to a DataGrid's validation summary manually. This is all working, but I can't find a way to retrieve the cell which contains the error.

I need a reference to the cell because I need to focus that cell when the user clicks on the error.

I know what the bound data item, and the property causing the error, but it doesn't look like there is a Rows property, or Cells property or anything like that on the Silverlight DataGrid.

Any ideas on how to retrive a cell??