My firm works with leading epayments and ebanking providers (etnasoft dot com). We have broad experience with both .NET framework (VB, C# etc) and web security. Some elements are being used in the leading retail brokerage platform in the US - SogoTrade.
Please call the number on our web-site and ask for Paul, lets discuss it further - your project is very interesting for us.
Thanks!
Paul
(paul at entasoft dot com)