As there was no reply from the original poster to my reply I guess it helped but cannot be sure.
Are you sure that it is a moodle issue? I do not see anything in moodle that gets 'inside' an Excel file, or changes the permissions of Excel. Can you replicate the problem from within college AND somewhere external, if not then it is not a moodle setting that is causing the issue. Has the professor tried some other method of transfer that works (email, file transfer, memory stick)?