We'd like to have time tracking in either a Story or its sub-tasks, but not both.
If an estimate has been entered in the parent, we prevent sub-task creation through a validator.
We'd now like to prevent estimating if a sub-task exists. The Behaviours and ScriptRunner apparatus does not seem to work on time-tracking fields. Is there any other way to say "if sub-tasks > 0, all time-tracking fields are read-only"?