Add stock back from Works Order - Further Explained

To be able to add an item or items back into stock from a works order / B.O.M. i.e. works order allocations call for 10 items but you are left with 3 items that are spares that can be re-stocked and used again. example, if we change a valve with a different handle we have to put the surplus handle back into stock via an addition. could this be done on one works order? Further Information. . . . . What I mean is for example, you have a works order for an item say a tap, now that is a complete tap, but the customer wants a different handle option on that tap. The works order has the complete tap and also contains the optional tap handle. The tap handle is changed over and the original tap handle is now classed as spare and now needs to go back into stock. How is this achieved without adding the original handle through stock control. It would be great if this was done all through the works order/B.O.M.