I have an application that needs to prevent a user from performing an
action until all other users are out of a specific table. I can think
of several ways to accomplish this but not of which is resistant to
abnormal database disconnects. I would appreciate any suggestions.

Example:

User A, B, C are entering payroll numbers for the month.

User D processes those number, but as a failsafe the system needs to
make sure that users A, B, C are not still entering numbers into the
table that User D is going to process. I don't want to prevent users
A, B, C from entering number but I want to tell user D that they are
still doing so.

Thanks,

Matt