WIP return in discrete manufacturing.

Dear All,

We are currently on 11i working on discrete manufacturing setup on Average costing method. Current Supply type is push and evaluating Assembly Pull. Would any body assist me in understanding how would a semi processed WIP be returned to inventory in pull and how would it be valued. Say the routing has 10, 20, 30, 40 processing stages. Some quantity is lying at stage 30 which needs to be sent back to inventory in push environment. Questions

1: How would this be return be valued and accounted.

2: Since there is no item code for such a semi processed item, how will i inventorise it?