How so send datagrid validation errors to view model

How so send datagrid validation errors to view model

I have a datagrid from the wpftoolkit. It is bound to a collection in a view model, and UI level validation has been implemented.

The validation works correctly, but I want to send the validation errors to a view model. I need to enable or disable controls based upon the validation status of the grid.

Just how do I do this?