Simple API program -- 2

there is site called : [login to view URL] , this is trading site for currencies... i need program that i can input into it that i want to sell/buy when price reach specific amount..and make loop into it. ex. USD/EUR : .5 , i need application to buy EUR with my USD if price go to .4 , and then sell USD again if price up to .6 ... details of API available on : [login to view URL]