I am having a problem with reordering rules with multi company. Currently the company setup is Parent, Child A, Child B

I want to define a global reordering rule that will check Child A + Child B for a product quantity (defined globally). Currently through the parent, I can see the total stock of Child A + Child B. Which is fine and works as intended, as the parent is supposed to monitor the Child company stock.

But I want to set up a global Reordering Rule. OpenErp forces me to choose the parent in the form, (which is fine as the parent is taking the total of Child A + Child B), but the problem is it forces me to choose a warehouse belonging to one specific company. This is preventing me from defining a global Reordering Rule.

Example: product , min quantity 200. Max quantity 200 Child A has 100, Child B has 50. Parent now has 150, because it is Child A + Child B. (parent does not have any physical stock)

the current reordering rule will order 200 when run from the parent company. Instead of 50 units. I want to make it order 50 because that is what is necessary to meet the global requirement of 200.