Survey123 connect mathematical expression

[OskarPenje1]

Hi. I'd like to create an expression to filter out choices based on an integer column in a linked csv. I want the user to get a shortlist of the 10 most common speices, based on the observat-column. The csv is linked from agol and will be replaced there from time to time. 

An additional functionality that would be nice in my case is having an autocomplete work on the whole list of species (136 items) but only display the top 10 most common species in the drop down. First thing just solving how best set up the filter expression for the dropdown (select_one); whether it should be as a search () appearance in the choice_filter column of the survey question row, or create a filtered subset using calculation in a separate row, and to reference that in the survey questions. Happy for any guidance I can get on this topic. Here is how my questions look (art=specie): 

[DougBrowning]

I think all you will be able to do is a text based comparison.  I would just have a column like TopTen and then have a simple X.  Then load all the species that match X.  You could keep the numbers in the csv just use a different column to find the matches.