Filtering by value parameter

We're embedding PowerBI reports in a web page, and setting filters from our own code. Main fact table is Event, which has a Date and a Duration (in milliseconds). Desired output is something like Date # of events % Standard 01/02/2022 34 95% ... 01/03/2022 193 100% ... ... % Standard means "percentage of these events that have a duration less than a value". Now, I can certainly CALCULATE, SUM and FILTER my way to doing so, except... That value is input from the user. It'll change from run to run. The user can put in 1ms, 55ms, 123456ms. How do I get that arbitrary value from the UI to somewhere I can get at it in the formula?