Calculate a different initial value based on enum selection

[elan_Bailey]

Is there a way to calculate the initial value of a date column, based on which option the user chooses from an ENUM in the same table?

Column timeline: allows the user to choose
3 Months
1 Year
3 Years
5 Years

If they choose 3 months, I want the By When Column to default to the initial value of TODAY()+90
If they choose 1 Year, I want the By When Column to default to the initial value of TODAY()+365
etc.

I’m just thinking that I could do this using an action once the record is added. But is there anyway to do this with one action or will I need to run 4 separate actions, each one checking for a different value?