Redmine

We use different task statuses, and we need to create a “primary effort estimate” field, which can be changed (or copy the value from “Time estimate”) as long as the task has never been in the “In Work” status, if the status has changed to “In work” and then changed again, for example, to “Estimation of labor costs”, the field “initial estimate of labor costs” should remain unchanged. How can this be implemented?