Hi Stephen,
thanks you this worked for me.
I've addopted it to my case, cause I have "Add child" in the each item, so the code looks like this:
Private Sub RadGrid3_ItemCommand(ByVal source As System.Object, ByVal e As Telerik.WebControls.GridCommandEventArgs) Handles RadGrid3.ItemCommand
If (e.CommandName = "InsertSubItem") Then
Dim editedItem As GridDataItem = CType(e.Item, GridDataItem)
editedItem.Expanded = True
editedItem.ChildItem.NestedTableViews(0).IsItemInserted = True
editedItem.ChildItem.NestedTableViews(0).Rebind()
End If
End Sub
Thanks again