Catch USSD Codes

I need some help to figure out a way to catch which USSD codes are executing in my phone. This is for a little project I'm working on, to simplify an app that my cell carrier provides, but I don't have any idea of what codes are executing some times, couse there are not documentation about it. I'm expecting something like a sniffer or similar, but I'm open to suggestions. My handset is a Xiaomi Redmi Note 5, just in case somebody knows a way to achieve what I'm looking for doing a trick in system settings or something hidden in the OS.