=== modified file 'stock/stock.py'
--- stock/stock.py	2013-09-20 11:24:37 +0000
+++ stock/stock.py	2013-10-01 09:55:08 +0000
@@ -1239,6 +1239,7 @@
         for pick in self.browse(cr, uid, ids, context=context):
             new_picking = None
             complete, too_many, too_few = [], [], []
+            temp_qty = 0.0
             move_product_qty, prodlot_ids, product_avail, partial_qty, product_uoms = {}, {}, {}, {}, {}
             for move in pick.move_lines:
                 if move.state in ('done', 'cancel'):
@@ -1278,6 +1279,14 @@
                         new_price = uom_obj._compute_price(cr, uid, product_uom, new_price,
                                 product.uom_id.id)
                         if product.qty_available <= 0:
+                            move_ids = move_obj.search(cr, uid, [('product_id','=',product.id),('picking_id','=',pick.id)])
+                            if (move_ids and len(move_ids) >=2) and complete:
+                                amount_unit = product.price_get('standard_price', context=context)[product.id]
+                                new_std_price = ((amount_unit * temp_qty)\
+                                + (new_price * qty))/(temp_qty + qty)
+                                temp_qty += move.product_qty
+                            else:
+                                 new_std_price = new_price
                             new_std_price = new_price
                         else:
                             # Get the standard price