MMC Buttons are too complicated. You can use the Remote Device, much more easier.
Choose Generic Remote, set Input M-Audio Oxygen. In the top table select Fader 1. Find MIDI CC, which is sent by pressing Play button on the Oxygen, and insert this MIDI CC to the Fader 1 Address.
Control name = Record
MIDI Status = Controller
MIDI Channel = 1
Address = XX
Max Value = 127
Flags R,
In the bottom table, set the action.
Control name = Record
Device = Transport
Channel/Category = Device
Value/Action = Record
That’s it.
Just set on the Oxygen, to send Maximum value of this button 127, which is set, but you have to set the minimum Value to the 127 too. This is because of the sending Value 127 everytime, you press the button. If you don’t set this, you have to press the button twice everytime. Once, it sends value 0, and makes nothing. Than it sends value 127, and it will wokrs.
Best,