In order to access customers you need them to have a VNC server installed. ViewerX is a client component that connects to a VNC server. So it's probably not exactly what you are looking for. We are working on a version of VNC server implemented as ActiveX component. This is exactly what you need. You could host such VNC server ActiveX on a web page, then a customer visits the page, the ActiveX gets downloaded and installed to his PC and establishes a reverse connection to one of your engineers listening VNC viewers. After connection is established, the engineer will be able to work with the customer’s remote desktop.
Should you have any questions you can contact me at yury@s-code.com