Here is a sample project that allows you to insert a "target date" using the correct format. If the date you enter is BEFORE the current date then you'll trigger the appropriate popup. If you enter a date AFTER the current date then you'll see a different popup.
How to use it and test it against a target date
The image below shows you the setup for the SHOW trigger on the button.
TIP: Select "Show Variables" in th View tab to see the variable names for system variables. You will need this name to use it in a Conditions statement. Example: sys.metadata.currentDate
In this example, "Target Date" is a custom variable that holds the date entered by the user.
You can also just code a date instead of the custom variable with quotes like this "2022/6/2".