This article shows how to lock individual assignments from updating.
Overview
You can lock forecasts and actuals on individual assignments for updating by using the Alocked field, which you can add to a custom view, or have your administrator include it in a standard view.
Fields related to assignments locks are:
Alocked – Setting this to “Y” locks the assignment from forecast or actual updates.
ALockedBy – Shows who last locked the assignment.
ALockedOn – Shows the date the assignments was last locked.
You can see the Alocked field in a view in the screenshot below:

For more on the types of data locks available in ResourceFirst, see
Data Locking in ResourceFirst.