configuring combinations

[Ipood]

I would like to sell batteries with the toys that I am selling. Since it is just an option, I can add the option but it doubles my stock number. All I want is to offer batteries YES or NO and YES brings cost addition. But how can I prevent my stock number to double?

[tomerg3]

Each combination has it's own stock.

You can check the following thread for instruction on how to make the stock reduced on all the combinations whenever any of the is purchased.

http://www.prestashop.com/forums/viewthread/43828/