Desktop submission software – Built into our database

I run a online directory submission site and wish to extend it to a downloadable software which will allow users to use the software from the desktop users will then be able to run the jobs from the desktop, the application must connect to our websites database to do all the jobs. We require it to be secure and also have a way of letting users know of upgraded versions of the software. the application must have a nice interface. we do need a website to sell this software from so if you are also a website designer we can also talk about the price of having a website designed.