I need a JavaScript event for submit button to make my own goal in Metrica manually.

I need a JavaScript event for submit button to make my own goal in Metrica manually.

Unfortunately, you cannot add JavaScript code in the form builder, if you need to run your own script then you will need to get the source code of your form to achieve what you want. 

This guide will help you to get it: How-to-get-the-Full-Source-Code-of-your-Form