How to select a maximum of 3 choices in a select_multiple question?

Hey all,

I have a question in a survey that reads something like, “Select the top three sources of funding for this project.” I’d like to offer users the option to select multiple answers, up to three. Is there a way to enforce that? In other words, is it possible to allow users to select up to three answers (which would also allow them to enter two, one, or zero as well), but would not allow them to select four or more?

try this:

${my_select_multi} constraint: count-selected(.)<=3

See count-selected() for details.