Combining with other stores

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I need to create a button that can send a different product id to a another site. The first thing I was thinking was to edit the sql table to have a "yes or no" for each product, kind of like the red or green circle if a product is enabled or not. To do this i know i need to edit /catalog/admin/categories.php to have a new red or green section if the product is linked or not. Then I know catalog/product_info.php needs to be edit so if the product is linked to show the button. I'm not even if this is the right section to be asking such a question but i'm not very experienced with php and I was hoping someone could tell me if i'm even heading in the right direction.