Add form submission to scheduling plugin

Hey, I have a wordpress plugin that organizes online scheduling. ([login to view URL]). It works fine, but I want to add another feature, which is to automatically add the visitor to a newsletter through the website user's autoresponder. (The main ones are aweber, getresponse and mailchimp). I'll retain rights to this plugin when it's completed. If there's any graphics needed for the job, I'll provide them. I also already purchased the plugin, so once hired, I'll give you those files. This is a small change to a working plugin, so I don't want to spend a lot on this project. If you do a good job with this, I will definitely have more work for the right programmer. Please keep this in mind when you select your price for the bid. If you decide to bid on this project, please start your bid with the words, "tripwire" so that I know you actually read it and understand the requirements.