Datagrid - How can I get the row number of parent row in a hierarchical grid.

[Shaji]

I have created a collection of my class
This collection has a hierarchy of the order
Batch -> Documents -> Properties
This is not a Dataset but a user defined collection.

I have bound this collection to a Datagrid.

Now when I am viewing the Properties for a Document under a Batch, how can I find the row number to which this document belongs? as the currentcell property returns the row/column of the current cell (Properties) & the CurrentRowIndex returns the row number of the Batch selected.