Someone could inform me on how to apply for promotions to my product using a discount module has a single product at places to apply to all products as does the current module?

I think taint the module to change the rules generate the module so that it can reconaitre field "entity reference" first place in my type of product promotions and list my selects the help button on / off. So the idea here is to create a field in the type of product and to compare rules thanks to the data field with that discount, if the value of the field corresponds to an entity discount is applied when the promotion in question .. . This is a somewhat heavy I count on you for sugestions Thank you ;)