Using "Stock Model" in manufacturing

In Creo 3 i can create a "Stock Model" to get the remaining material after a NC Sequence.

How can i set it as Real stock for next sequences?

For example: first sequence is a Volume Roughing with a tool dia 20mm

I would like to create a new volume using the same mill window but limiting it to the remaining material of first sequence

I don't want to use Roughing and Re-Roughing :-D

I cannot replace the starting workpiece with his worked component of the familytable inside NC

I can save Stock Model as prt or stl, why i cannot use it for example for further operations?

Thanks a lot

Osvaldo