Give copy permission without execute permission

Hi Everybody,
I have a small windows server 2003 active directory network, I have a
network share
directory with some files shared for everybody, how can I give permission on
this directory
to let users copy the file to their client computer but not open it directly
from the share directory?
I don't want them to just click on share file and read it but able to copy.

Second question:
If a share file on network locked by a client machine how can I release it?
I mean
Sometimes people open the document directly from the share directory then
nobody else can
change the file (Rename/delete,...) even the Admin, It seams that it's
locked by the client?

Thank you in advance - Sam