Need a plugin, very simple one

I need a plugin that would take care of the simple solution on this page: http://kwakster.com/wordpress/

One line of code needs to be placed in the post, below the content and above the meta or comment template.

Obviously this is not a tough plugin to create, but I have never worked with WP plugs. If anyone could give me a link to a page that includes a hook or other needed info that would be great. If anyone would like to take on this plugin or add our button to their existing plugin that is also absolutely good with us!

for more info or questions email me: bminternetservices @ gmail.com