Create a semi-API based desktop application

Hello there! My project that I need completed is what follows. I need a program that can instantly send a message on a trading site that I use as soon as that person opens a trade with me. Their API does not have a message feature but it does have trade grabbing features. It would be much easier if the API had a function to call to do such a thing but I've contacted the company and they don't support it via API access. So I need someone to develop an alternative method. I will have this program running 24 hours a day, so it needs to be fully sustainable. Design of the program is not really an issue, if it runs and works as needed then it's good enough for me. Info on what I do: I trade actively on an exchange site, people open offers with me when they see my ads up. I usually have 300+ customers a day and I don't have time to send them my premade message every time, it's just getting to be too much work. I need a program developed that as soon as they open that offer a message is sent to them so they feel welcomed and as if myself had messaged them. Please add me on skype so we can discuss this further! Price is not set and will vary.