Auto populate subform row field

Auto populate subform row field

Hi there!

I am having trouble working out how to write script to auto-populate a field in a subform based on the input of another field in that subform. I wrote the below script but it only seems to be applying to the first row I add to the subform and doesnt apply to any that I add after that.

input.Attendee_List.Age = yearsBetween(input.Attendee_List.DOB,today);