Hi,
I can do this pretty quickly with a custom module. Please answer the following questions so I better understand the requirements:
1) if "qty 2" is decreased, will "qty" also decrease?
2) When qty decreases and qty 2 decreases as well, will this only be from order actions?
3) if "qty" increases, will "qty 2" increase? In other words, if you go into the admin and manually enter the value for qty will qty reflect that? Another possibility is returns. If an item is returned, will the qty increase in qty 2 as well? (this is possibly not a concern)
4) If the item is out of stock according to rules of "qty" but not "qty 2," What is the course of action?
I've been working in ecommerce for years now, so there are always scenarios that need to be considered before coming up with a solution.
Regards,
Matt