Comment 6 for bug 677257

Hi Claire,
The last time I looked at the scheduler code, tasks could only be triggered by the clock, not by events. Some entities like production orders, sales orders, and invoices can trigger code from events using the workflow, but products and bills of materials don't have workflow.

This isn't really a good place for asking questions like that. You'd be better to ask them at http://www.openerp.com/forum/ or http://stackoverflow.com/