[vtkusers] Getting the original cell id's from vtkExtractUnstructuredGrid

[Sarah Macumber]

Hi all,
 
Is there anyway to get the original cell & point ID's from vtkExtractUnstructuredGrid which returns a new vtkUnstructuredGrid?  For example if you extract the cells using extents in the middle of your dataset how can you find out what those cell & point ID's are?  They get re-ordered in the new grid.  I am not doing extraction via graphical selection so I need to use global cordinates to do my extraction & then get back an ID list of the cells.
 
Any help is appreciated, Sarah