Dynamic repeated question based on question asked before in the survey

1. What is the problem? Be very detailed.
I am currently designing a household survey using ODK and I am quite new to the ODK community.

In my survey, I first ask the age of each member of the household. After a number of questions I want to ask questions regarding their tobacco and alcohol consumption but I want these to be repeated only for individuals who are 20+ years. I have then created a repeated question group for each individual in the household but I am having difficulties in making only people who are 20+ to appear.ODK_example.xlsx (11.1 KB)

I have tried different things with not much success:

  1. I have added a relevant statement at the begin of repeat group asking to repeat only for age>20 but it gives an error when transforming the xls file to xlm.
  2. I have created a new group with the relevant statement but I also get an error

I have attached the xls form to this post for you to have a look. Any help or ideas would be greatly appreciated!

Thank you everyone in advance,