To time stamp a cell with the current time without it updating constantly, follow these steps:

1. Select the cell where you want to insert the time stamp.
2. In the formula bar, type
   Formula:

   "=NOW()" 

   (without the quotes) and press Enter. This will insert the current date and time in the cell.
3. Right-click on the cell and select Copy from the context menu.
4. Right-click on the cell again and select Paste Special from the context menu.
5. In the "Paste Special" dialog box, select "Values" and click "OK". This will replace the formula with the current time value, which will not update automatically.

Now, the cell will display the current time when you first enter the formula, but it will not update automatically. If you want to update the time stamp, you can simply repeat the steps above to insert a new time stamp.