Build a script/software for based website

i need a script or a software for the website called opskins.com. in the website you sell in game items of counter strike for real money but you can send only one item each time. i need a script/software/extansion that will be able to sell alot of items quickly (i will be able to set a price by % of the reguler price) it has to accept trade offers from the website with steam aswell. i don't know if its possible to make but if its do just bid :P