TimeSheet Locking?

[MartyP]

Is there a way to batch-lockout everyone's timesheet's? Similar to the
'Send Timesheet' button/action.
In our organization everyone enters their own hours (500+ emps).
We would like to allow employees to modify their hours throughout the
month but lock it (no more entries) at the end of the month.
Current Choices:
Option 1) All emps always use 'Send Status' every week. Problem: at
the end of the month we have to remind everyone to use the 'Send
Timesheet' to lock their timesheet so that it cannot be modified.
Option 2) All emps always use 'Send Timesheet' every week. Problem:
this will lock each emps sheet at the end of each week. If mods need
to be made later (before the end of the month) then the Project Admin
will have to unlock the sheet and make the changes. THAT could be a
lot of changes.

Best Solution (How to do this?):
All emps always use 'Send Status' every week. Then the Project Admin
locks all sheets from modification at the end of each month. There
are too many emps to click 'Send Timesheet' for each emp so a batch
process would be great so that we can lock ALL sheets all at once.

Any thoughts?
Thanks,
Marty
PS - I am not a Proj Admin...just helping out the dept.