How to set value for a dummy question

I have an "Age" question, with type number like this:

Then I want to convert these number into some groups of age, such as:

How to do?

- First, create a single question "D_AgeGroup" right after "Age" question, with such options:

- Then, set D_AgeGroup become dummy question on Properties tab

- Finally, go to CGScript tab, write cgscript for setting D_AgeGroup from Age

You are done.

On viewer, when clicking next at Age question, value of D_AgeGroup will be set