two warehouses

Hello,
there is any solution for sync a new warehouse to opencart ? i have an external warehouse that i would like to allow opencart to read. So, the quantity of products avialable will be (quantity + quantity of external warehouse).
The solution: sum the quantity of warehouse with quantity in opencart is not applied, because we need to keep separate the two quantity fields.

If there are any module will be better, because modify all opencart model to allow to read quantity with this new wule is not a good thing.

Thank you for your help
Aldo

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