Help integrating a form into third party API

Hello Freelancers, A) I have a contact/booking form fully working, it checks inputted data for errors using PHP / Javascript, returns error / success message to the user upon submit and sends an email to the admin about the completed form. B) On this same form I have added some hidden input fields in order to send some of the data into a third party API database. I have a problem in that method "A" above is submitted as follows (<a href="javascript:submitForm();" class="btn btn-large btn-info">BOOK NOW</a>) and doesn't submit the data into the API. Method "B" when submitted as follows (<input type='submit' name='submit' value='submit' />) does submit to the API but it doesn't do any of the form checking, error/success message or send the email to the admin. I need you to create one submit function that integrates both method A and method B so that the data is submitted to the API and the form is checked and emailed to the admin. I need an immediate start on this project please. I look forward to hearing from you with your proposals. Work will need to be done on my development site. Thanks, James.