Lock cells after Today's date passed (VBA excel code)

I am new to this forum so hello to all.

I am trying to lock cells after today's date has passed so that no one can make changes to it after today's date has lapsed. This is for protective reasons so that people do not remove their names from reserving something after using it. Now the code should disallow locking after cell input entry when today's date hasn't passed so that changes can still be made by the user. I am trying to determine the code to do this but I have no idea as to how to do it.

Here's a scenario: I reserve something for Aprill 11, 2009. I input my name. Since it's April 9th, 2009, I am still able to make changes up and until April 11, 2009. After this date, the cell is locked and no changes can be made, except for the administrator.

Also, a code to allow the administrator to make changes within the cells if need be. That would be appreciated.

Please advise,

Thank you