Custom JQL function

Hello, I created a custom JQL function that gets the values between 2 numbers in a custom field
My function works when I do the following:
issue in customFieldBetween(5, 10)
However when I try to run
myCustomField in customFieldBetween(5, 10)

It detects the “myCustomField” name and runs correctly in the background and it finds results however it is not displaying anything on the UI

How can I make it possible to put something different that “issue” before the “in” ?