I know how put content to and retrieve content from the clipboard.
However, between these two operations, it is possible for another operation to change the content
All I could find was a Clipboard Monitor written in C#/VB.NET. I see WPF and WinForms, so I assume this is a viable options.
Involves pinvoking some methods from the user32 dll.
At the time of edit, the original link above is broken. Here's an archive.org snapshot