You would need to use a variety of components that are configured to be visible only if your number values are valid. I did something similar in my experiments app:
@Robert_Petitto’s ideas might work if you make the user enter ages first, and if the data is valid (simple math between the ages to calculate a value that’s above or below zero), then show a form button. Then use the column values to pull in the entered ages from the previous screen.
No I’m thinking like your example where the entry fields are on a detail view screen. Instead of your list showing it showing a message, it would show a button. Right now you can’t do the calculation in a form because the data needs to be written to the sheet first for the glide math column to work.