Overwrite product status within a plugin?

[Cybex]

Does anyone know how to overwrite a product status (active - inactive) within a custom plugin?

For example: when I do this, the product is still active: $vbulletin->products['my_product'] = 0;

I need to know this, because I have two forums (on different domains) linked to the same database. So users only have to register once, but on the first domain I want product x enabled and on the second domain disabled.

I already have a product that takes care of the categories, etc. So I only need to know which variable(s) I need to change to accomplish this.

Can anyone help me out?