505 workshop security

We have about 10 different techs that use 505workshop to program over the network with ethernet to the plc. My problem is that recently we had two people trying to edit the same program at the same time and the plc lost its program. My question is this. Is there some type of security or possibly a bit in the plc that would let us know if somebody else is already connected to it? Or is there another solution to this problem? Any and all sugestions are welcome.
Rodney

We will be implementing RSMACC and this is one of the reasons. Prior to this though, our method was to keep the latest copy of what is in the processor on a network folder. The network was backed up daily on tape by IT and kept for 30 days. If anyone wished to communicate with a PLC, they would open the file in program backups (our folder) that was the latest and greatest. If they made any changes, they were to save the file in the same place they got it with the day's date in the name. (PLC_5-17-06). In the same place where the PLC's latest file was kept, we also had a history folder. When a tech made a change, they would save the file as above, and move the program they started with into the history folder. This was our method and it worked fairly well. If anyone had the latest file open, when someone else tried to access it, you would be told by windows that it was already open and be asked to use a read only copy. If a person saw that message, they new apparently someone else was using the file and that they were not free to just change it at whim. This worked pretty well, but I think RSMACC will be even better.

Russ