You will have to some of your own research and code experimentation. I will assume that you have a "main" table for holding the basic information. Create a logical (Boolean) field in that table. Set it so that when it is "false", any form that opens a record will allow field editing. When "true" all the fields in the forms would be "locked". You would do this test in the forms "On Current" event.
You will also need to use the "Datediff" function to compute whether the logical field is set to true or false. This can be done through either a forms "On Current" event or through VBA code. Your choice.
Technically, setting the logical field on the forms "On Current" event would not be considered optimal since it would duplicate the function of the logical field. Doing it through VBA code allows you to set the value of logical field at a time of your choosing.