Updating ActiveX Controls

[Biblin]

I'm somewhat new to publishing ActiveX controls over the web so I may be
doing something silly.

I have an ActiveX control which is shipped with a couple of dlls in a signed
cabinet file. It downloads fine and runs fine... lovely.

However if I update the control, increase the version number in the inf file
and replace the cab file on the server, it won't update on the client PCs
when they visit the page next but instead, keeps using the version that's
already on their system.

How do I get it to automatically update without the users having to delete
the control from the PC's manually?

Thanks