perpetual inventory accounting

for details on perpetual inventory accounting see the examples on this link
http://accountinginfo.com/study/inventory/inventory-110.htm

I checked the account_anglo_saxon module now and it works perfect with only one problem. In perpetual inventory system the product that is for selling only should have expense account set. But on product form as soon as "Can be purchased" checkbox is unchecked then Expense Account field becomes read only. So this needs to be modified so that user can set expense account for product that are only for selling and hence perpetual inventory system would work correctly.

Also the module description should clearly mention that it installs perpetual inventory system. It could become useful for a lot of people.

Thanks hda (OpenERP), that solved my question.