It looks like you want a one-way operation to easily lock the contents of a given cell (but not to unlock them). I can’t see any other function that the checkboxes are supposed to perform.
Firstly, I will say that there is almost certainly a much, much easier way to accomplish the basic task you are trying to perform here. I say this because your question is far from the usual requirements for an Excel or Calc sheet. If you give more information on what you are basically trying to accomplish, it may be possible to recommend a much simpler route. (i.e., what were you trying to get Calc to do that led to the need for these checkboxes? What was the original, simple idea of what you wanted the computer to help you with?)
However, I will attempt to answer your question as asked.
The only way I am aware of to lock a cell’s contents so they cannot be edited is by protecting the sheet it is on. You do this by selecting Tools->Protect Document->Sheet… and clicking OK. (The default settings are usually what you want.)
By default, this will mean ALL cells on that sheet are protected. It is more usual to need to UN-protect one or two cells than to need ONLY to protect one or two cells. However, you can get around this. You just unprotect all of the cells before you protect the sheet:
- Select the entire sheet. (Click in the upper left corner of the sheet, just to the left of “A” and just above “1”.)
- On the menu, go to Format->Cells…
- In the “Cell Protection” tab, uncheck the “Protected” box.
- Click OK.
- Select Tools->Protect Document->Sheet…
- Click OK.
The sheet is now ready for use.
When you want to protect a particular cell:
- Go to Format->Cells…
- Check the “Protected” box in the “Cell Protection” tab.
- Click OK.
You will not be able to change any cell back to “unprotected” without unprotecting the entire sheet first. You can set a password for the sheet protection, if it’s important to have your “individual cell protecting” functionality be truly one-way.
(If this answers your question, please click the green checkmark.)