Permissions to deny users from moving a folder

We are running Windows 2003 Server Standard and have a folder which is accessable to all users called "Groups".  Inside the "Groups" folder, there are two folders, one called "Sales" and the other called "Marketing".  Permissions on the "Groups" folder are such that Modify and Write are not allowed for the users.  Delete is denied, and the following are allowed for users:  Traverse Folder/Execute File, List Folder/Read Data, Read Attributes, Read Extended Attributes, and Read Permissions.

The idea is I don't want users to "junk up" the Groups folder by creating all kinds of other folders and files in it.  All employees should be able to create new files, delete old files, and modify files that are located in either the Sales or the Marketing folders.  Someone in the Marketing dept should be able to copy a file from the Sales directory to their own (and vice versa).

The problem is, occasionally someone clicks the Marketing folder and drags it into the Sales folder.  I do not want them to be able to do this.  They should not be able to move the Marketing or Sales folders themselves, only the files contained within those folders.

I tried modifying the Sales folder for example with Deny (this folder only) Write Attributes, Delete, Change Permissions, and Take Ownership.  I tested and Sales could create files in either folder, but when they dragged the Marketing folder into the Sales folder it left the original Marketing folder, but the original Marketing folder was empty.  There was a "Marketing" folder created in the Sales folder, and all the contents of the original Marketing folder were there.

How can I prevent users from dragging the Sales folder into the Marketing folder and vice versa?