You will require to use Web Schedule module along with Web TimeSheet Time & Attendance edition to achieve this.

This module allows supervisors to schedule when employees are expected to work. Schedules help supervisors ensure adequate staff coverage and monitor whether employees are working when they should be.

Using Web Schedule module, one can create a schedule for each user.

  • Click on the Schedules icon at the top.
  • Select User Schedule from the left side pane.
  • Click on the date to schedule a time for the user.

Scheduling Activities and User Defined Fields:

To select an activity to associate with the schedule time, click a schedule entry and enter a value in the Activity field of the window that displays. Activities must first be created and enabled for the schedule user in their user profile. You may also define values for Timesheet user defined fields using this window.

Enforcing Scheduled Activities:If the schedule user uses a timesheet, you can specify that the activity and/or Timesheet user defined field values you choose must be entered on the user's timesheet for the scheduled time.
To do this, enable the Enforce check box(es).
If Enforce is enabled and the field value entered in the timesheet does not match the value you specified, a scheduling discrepancy will be reported on the user's timesheet and in reports. The same can be done while creating scheduling templates.

Summary:
Using the Scheduling tool, you have the ability to enforce the Activities and User Defined Fields for each user. Once you schedule the user, you have the ability to enforce the Activity and User Defined Field that needs to be entered on the timesheet. Once this is enforced, a scheduling discrepancy will be reported on the user's timesheet and in reports if the time is not entered against those Activities and User Defined Fields.

Refer attached screenshot: