Change date in a cell when value in other cell changes

I don't know if it's possible but for a large sheet I would like to have a column in which the date changes when I change a value in another cell. For example there is a cell called Transport: Planned / Executed

I have filtered my sheet, so when I choose the option"Executed" (in the drop down menu "Transport") the specific line wil no longer be visible in the sheet. The sheet displays only current data. What would be nice if I could add a column and use a formule that when the cell "Transport" is changed into "Executed" the date cell automatically fills in the date today and then never changes it again. So this entry should be static.

I found a formula "today, but whenever I open the sheet the date changes in the date of today. So if I would mutate a cell into Executed today it should say June 3, 2024. And when I look at it tomorrow again, it should stil show June 3, 2024 and not June 4, 2024.

Any tips ?