Generate a single select list based on filter condition

I would like to generate a single select list that is linked to a roster question (this question list the members of the household).

Within the roster, the date of birth for each household member is captured. Using variables, the age and birthday are calculated and stored for each household member.

The single select list should show the single household member (or in the case of twins etc, then more than one household member) who has the next birthday after the interview date; if two or more household members share the same birthday and are not twins (or other multiple birth types) then the oldest member should be shown in the list.

Code Sample
Select Next Birthday: selectedBDay = Members.Where(x => x.BDay > Date).Select(x => x.BDay).Min()
Select Oldest from List: selectedAge = Members.Where(x => x.BDay > Date).Select(x => x.Age).Max()
Filter Condition for Single-Select Question: (BDay == selectedBDay) && (Age == selectedAge)

I tested the questionnaire with this code and it was able to generate the list. However, it no longer generate a list of the household members that meet the condition.

Please note that the selected member’s birthday may also fall in the next calendar year.

Can I get some assistance?

The method is used to force the enumerators to select persons randomly in PAPER surveys.

Why would that be necessary in a CAPI survey?

This is the selection method used for this survey.