Drag & Drop Folders - How To Stop Them Expanding?

Is there any way to prevent a folder from expanding (to show its content) when another folder is drag/dropped into it?

We use the folders to record the progress of a sale: Sold Folder, Paid Folder, Despatched Folder (then to archive) but as we move a sale from one folder to another the folder expands to show its new content. Really annoying!

Any help gratefully received!