Same quantity and price for products on different sites.

Hello, I need same quantity and price for products on different sites.
I have sites with same products, these products have same models, but different description, titles, structute and e. t. c.
1. I need change price and quantity on all websites, when administrator of main site update information, each time.
2. Also I need change quantity on main site, when buyers do orders on each site.
Maybe somebody to know solution for this, or your ideas?