How can modify Product Info page to Contac us Form?

I need to modify Product Info page when product select is ID=141 (for example).

When product is ID=141 (f.e.) i want to appear a Form like Contac Us, so the customers can write in fields. Then customers need to pay.

If product ID is not 141, i want to appear a Product Info normal page.

How can i do that?

Thanks

Probably the closest would be to set your test input fields up as product attributes. This wouldn't be exactly what you are looking for, but what you want is not really possible (i.e. two different actions: submit contact form and pay) or would require lots of custom coding.

Here's a link to the relevant part of the FAQ.

But i cant put in the code:

if (Product_Name == 'A')
{
copy the code of a Form (like Contact us)
}
else
{
the same code in the product info
}

??? Where can i put that?

You could insert redirection code like that in the includes/modules/pages/product_info/header_php.php for each product type that you are using, but that wouldn't actually deal with you issue of also getting customers to pay.