eBay API .NET development Needed

Budget: $100 to $500

Greetings valued freelancers, My name is Nabeel and I am a seller on eBay. I have started a small application which grabs data automatically from eBay making some of my manual tasks on eBay automated. This software is also marketed, however the application is underdeveloped and is in PHP therefore, it's not making much progress.
My previous programmers are very slow at their work and it has been a while now and no work has been submitted from them. 
What I'd like to develop is a platform such as www.auctiva.com or www.pushauction.comThese are very complicated to understand if you are using them for the first time; I'll be providing you account details and account details to eBay developer account.
You should be good with APIs and .NET
eBay is a platform to buy and sell. Sometimes sellers have 100s of orders a day and manually preparing shipments can be very difficult therefore this task must be automated and made easier. There are some unnecessary clicks involved on eBay which can also be eliminated using this application which further saves some time.
I don't have any targeted country from where the programmer should belong too. My budget is slim, I am not able to pay a lot of money for this, but I had in my mind to pay in steps as the program is being developed. This way you will get your fair pay and I get to see my software being developed before paying. ( I have been scammed by my 1st programmer )
I have my own hostgator baby plan account and can pay for some additional expenses.
Payment method preferred would be Paypal. But I can also pay using oDesk or other forms if you are located in a country which does not accept Paypal.
Contact me with your offers and skills. I will then give you a detailed overview of what is required - I will be explaining the tasks using teamviewer so you will understand each bit perfectly.
Best Regards