Thanks @mathieubossaert for your reply !
Yes I can share xlsform !
Solution :
test_choice_filter.xlsx (13.6 KB)
Solution (with a "dynamic" repeat-count, according to this) :
test_choice_filter_with_limit.xlsx (13.8 KB)
Unfortunately, I'm wondering if it's possible to limit the number of repetitions. With the second form, I only fix the number of repetitions. I would like to have someting like '.<${Q1_length}' but it looks like impossible or seems to be a very bad way. Any idea ?
Thanks again 