Nested DataGrid with inner datagrid in rowdetails template

Hi,

I am using nested datagrid with inner datagrid in my rowdetailstemplate. I am able to get functionality of tree structure using nested grid. Inner datagrid has multiple rows with one of the column as textbox defined inside <DataGridTemplateColumn.CellTemplate>. This textbox has lostfocus event which is firing properly.

Problem is when inner datagrid is expanded and textbox control is changed on 3rd row. I am not able to get correct value of innergrid.selectedIndex property (correct value should be 2) it is always zero.

Help required thanks in advance