...return the difference between two absolute paths?

For my project, I need to pass two actual paths to a function so I can set the relative path of the second actual path passed.

For example, if I pass c:\folder1\ and c:\folder1\folder2\folder3, the function will return folder2\folder3 - as this is the difference between the two. This makes it easy to link to my second path relatively from my first path, if you see what I mean.

Thanks for any help,

Jim