share modes /locking in samba

[Fraser Campbell]

A client of ours is interested in sharing data for an DOS accounting
application to Windows clients (98, NT, and 2000) via Samba on a Linux
box.  Their file locking does not seem to work.

The application is written in MS Basic Professional for DOS version 7 ...
not precisely certain of that but it is a DOS Basic.  Their lock call
doesn't seem to actually put any lock on the files.

They wrote a small test application that simply opens and locks a file. 
They want all access to the file blocked (read and write) but the share
mode remains DENY_NONE.  Oplocks show up as BATCH+EXCLUSIVE but their
application doesn't see those (I believe they are Windows specific).

"share modes = yes" is set.  I've tried numerous combinations with other
locking options to no avail.  Samba version is 2.0.5a, running on Caldera
OpenLinux 2.3, Linux kernel 2.2.12 (IIRC).

Is what they are trying to do possible?  I should be able provide
additional details on the environment if necessary.  Hints appreciated,
TIA!

Fraser