Excel .tmp files not deleted

When our users open excel files on the shared network drive on our server, files are created with the .xls~***.tmp extensions in the same directory as the original file, and they are not being deleted. When the excel file is saved another .tmp file is created.

The files can be manually deleted. These are rapidly filling up the network folder and cluttering up the structure confusing users. I know a script could be written to delete them, but this is not an ideal solution

This problem has only just started happening and it is getting worse as more users are begining to experience the same problem, and complaints are coming in very fast.

Any heros out there with a solution to stop these files appearing in the network shared folders in the first place?