[totaltec]

There is not a simple answer unfortunately, what you want to do is going to require some in depth knowledge of Javascript and smarty templates. You could probably accomplish this with product options. But it won't give you a checkbox.

I would first setup a custom field using the extra fields module. Then write some code in the product page template that checks if this field has a "Y" in it. If it does you display the checkbox. Forcing them to use the checkbox is where the Javascript knowledge is going to be necessary.