As others have said, this is a time syncronization issue which is not Samba specific.
When the file is saved to the server, the timestamp put on the file is the Server's time. Assume for a moment that the server time is ahead of the workstation time. Visual basic will periodically check the timestamp on a file. If the time is newer than when it last wrote to the file, someone else modified it - hence the "This file has been modified outside of the source editor." In otherwords, if I last wrote to the file at 6:00, and happen to take a look at it and it says it was written to at 6:01 then I can only conclude that someone else wrote to it. If the server is 1 minute ahead, then it will save the file with a timestamp of 6:01 if I save it at 6:00WT (Workstation Time). That's where your error message is coming from. Novell builds time synchronization into the workstation clients to prevent these types of problems. There's no way to solve it only server side, otherwise it would be part of Samba, Windows NT, NetWare, and pretty much every other NOS.