static column content - calc

How can I determine what input can be entered in calc column. Example: Su(Sun) Mo(Moon), Ma(Mars)… . So column must be entered Mo or Su… but nothing else then those.

Needed for creating row filterable column as dropdown. So that the person entering the value does not enter anything else then those values to column.

Did you read a bit (‘Help’ at least) about ‘data validit6y’?

Sorry I am new in hire and had no idea how to search about what i needed. More precisely i did not know if that is even possible to do in calc.

That’s no problem. Please feel free to come back with additional questions if the help seems insufficient to you. (I didn’t intend to criticize you. My English is poor, however …)