Hello maisen20 and Pether,
I found these code by pairing the Flirc with an old remote control, and tested all the possible number for the command record_api xxx 120 (from 0 to 255).
For the Back/Exit command, I found just one command number (flirc_util record_api 70 102). Sorry maisen20, I did't found the back specific number.
For the OK command, I found two command number (flirc_util record_api 65 102 and flirc_util record_api 132 102)
I don't use Netflix, so I cannot confirm if it works, but you can try the second command for "OK" flirc_util record_api 132 102