Well, the very first obvious thing I see is that you want to be able to submit these items directly to Google, nextag, Pricegrabber, and Amazon.
You must understand that for each one of those products, you will A) have to have an individual account set up with them B) create separate interfaces, meaning for each product you have to write a custom routine to interface directly with their individual API implementation. I checked Google and Amazon real quick and they both have API's(I have used Amazon's API's before to implement solutions).
Secondly, I will have to ask further questions as far as if a web based solution is the right answer. I say that because ideally you want to transmit as many products as possible at one time, as such using a webpage to "keep" that connection open can become problematic when the volume of data that you are passing is large.
Other than that, I am extremely comfortable in both VB and SQL.
Look forward to hearing from you.