Classified posting software

We operate an automotive classified website. One of the tools we are developing is a manual posting tool. Our users have the ability to take an ad generated on our site and automatically pre-fill that same ad into other classified sites within seconds. How it works is, after a vehicle is listed on our site the user has the ability to post that ad to other sites with all the photos and html included without having to copy and paste anything. Here’s the sequence of events: 1.)Post vehicle to our site 2.)Click the “publish” link 3.)Choose the ad template and website you want to post in 4.) Our site opens up that website window and populates the ad for the user 5.)User clicks continue and solves the Captcha The issue takes place between our system populating the ad and then the user clicking continue and solving the Captcha. This is an issue because the other site sees our IP address when our site opens the new window and populates the ad. Then the user takes over and finishes the ad with their own IP address. Some filters don’t like the double IP address and half our ads don't get posted. What we need: After our site generates the ad we need a way to copy and paste that info into the corresponding locations (Title, Price, Location, Description, and photos). All the communication with these other sites need to look like it’s coming from the users IP address and nothing is coming from my servers.