Browser Alert for Right-Click on Image

Does anyone know of a window alert script (browser message) that would make an alert appear when a user right-clicks on an image? The idea is to warn someone that the image is copyrighted, or that they need to cite the source if they want to use it, etc. If such a script exists, is it possible to do this for just a specific image or images on the page, rather than a right-click anywhere on the page? Thanks for any help.