Validation Condition on Child's age

Hi, I have a household (HH) roster as below, and would like to include a validation condition on age that restricts child’s age to be less than that of the HH. head. how am I able to do this? I tried various LINQ expressions but none working. Thanks in advance.

Eric

You can get some inspiration in the public example of a household roster that contains multiple validation conditions for age & relationship to household head which you can find here..

Hi Peter, I am so much grateful.

Best