Activate one product when another is selected

I have been searching, but can't seem to hit on the right words.

I have a product that is an add-on to another product. But they can only purchase the add-on once they have selected that they want the main product. If that possible?

Make it an attribute to the first

Great idea, please explain.

The tutorials link at the top of this page is a resource
I searched for attributes
https://www.zen-cart.com/tutorials/index.php?article=57

Kobra,

So yo are saying just make it an attribute, not a product?

What about this scenario...

As you state, the purchase of product B is allowed only on the purchase of product A.

Today I purchase Product A, but decide not to purchase product B at this time.

3 months later, I see a need for product B.

I already have product A (3 months ago), so I only need to purchase product B this time.

But your shop makes it conditional that I have product A selected before I can select product B...

To get round this, you would have to have some way of getting ZC to look through the customer's order history and if there was a successful purchase of product A at any time in the past, then product B could be ordered.

An attribute system would not address this scenario.

current zencart attribute system dose not have attribute dependency feature.

what you are asking is the dependency .. what i did found is that few site have used two modules to create dependency for their attributes.

look at the following modules in free add on section .

Stock by attribute and
Dynamic Drop Downs.

those working together , should allow you to set dependency for your product.

you may also want to read following section before installing dynamic drop down

http://www.zen-cart.com/forum/showthread.php?t=93823

hope this helps

Thank you I will give that a try