Add button that leads to new page on product page

version 1.3.9e

here is my product page
http://fivariva.biz/zencart/index.php?main_page=product_info&cPath=1_5&products_id=21

in the page there is the "write a review" and "tell a friend" button
i want to write my own button that leads to an external page.
how do i do that?

Just use the "product URL" field in the product creation page. This will display "For more information , see this products webpage" at the bottom of the product info page. You can edit the text definition to a button image if you like.

but then i will have to do it for every page. is there a way for me to just edit something once and it will appear on every product page?
it actually leads to my own contact form, because i had problems setting up the email system in zen cart.

You could hard-code a link in /includes/templates/your_template/templates/tpl_product_info_display.php, if you don't want to paste a URL into a box for each product.