Different product , different signup form

Any idea how I can link for product I have to a specific signup form ?
Assume I have three products and I want to link each to a specific signup form , I tried to make products group and I created the forums , but when I try to sign for a new product it always redirects me to the default form

Which version of amember are you using?
In v3.x you use price groups, then use the link maker.
In 4.x you use the signup form system.

David