Returning a 'virtual' path with CKFinder

Using ASP.NET, I've got my images physically stored at this location:

/App_Data/content.site1/images/

I've set '/App_Data/content.site1/' as the BaseUrl in config.ascx, and CKFinder can browse through all the images without a problem. However once in the content the images are served with the base url of''/content/images/' so that's what I'd like CKEditor to end up with. Is this possible, or do I need to write a custom GetFilesCommandHandler (or similar) to achieve it?

Thanks