I am looking to have a website built, but before I start contacting various web design companies I wanted a question answered. I want a website built where sellers will be able to sell things; this will be for a very niche market. However, I am wondering if I can have the option for sellers to be able to use UPS / FedEx / USPS directly on my website to print their shipping labels. Is this something programmers / web designers are capable of building or is this not a possibility?