Conditional locking based on time value entered in another cell

What's a cell lock? By default, cells are all locked but that has no effect unless the Worksheet is password protected. What happens if macros are not enabled?

We need to know a little more. Is it only Cell B1 you want locked or is it anything in Column B with a date / time in Column A? Entering 3 AM isn't enough. It also needs to be accompanied with a date. Otherwise it's 3 AM on January 1st, 1900. This task could probably be accomplished with a workbook open event at a minimum for times that expired between workbook saves. I'd probably use a Selection Change event to see if the currently-selected cell is still editable.

Attach a sample workbook. Make sure there is just enough data to demonstrate your need. Include a BEFORE sheet and an AFTER sheet in the workbook if needed to show the process you're trying to complete or automate. Make sure your desired results are shown, mock them up manually if necessary.

Remember to desensitize the data.

Click on GO ADVANCED and then scroll down to Manage Attachments to open the upload window.

I noticed that you put in 3:00 AM, January 1st, 1900. A time alone is not good enough data. You also need to enter a date: e.g. 5/25/2017 3:00 AM.

Here is my shot at it. When you enter a time in Column B, the program automatically adds the date in Cell B1 to the time (unless you enter a date and time in the cell - in which case, it accepts it). This means the application is pretty much limited to a single date.

The second part of the program kicks in when you select a cell in column B to update. If it is within the time specified by Cell B1 on the control panel sheet, you can change it. If it is "expired" the cell is locked and you can't change it.

This spreadsheet makes use of locked cells and protecting the sheet. I have unlocked all cells in Columns A and B. Column B cells will get locked as appropriate. If you need other cells unlocked, you are on your own.

P.S. If you are going to use this as a template, unprotect the sheet. Select the range of cells containing this test data and delete the contents. The program doesn't fire if more than one cell in column B is selected. Then you can edit the sheet with new tasks and times. The sheet will re-protect when the first date is entered. The program also doesn't try to lock the cell if the date cell is blank, it will only add the date to whatever time you enter.