How to activate the microphone - BCD3000 with Mixvibes 7.21

Hi,
can someone tell me how is the MIDI command to activate the microphone on Mixvibes 7.21 with the "Ext A" button on the BCD3000.
Thank you.
can someone tell me how is the MIDI command to activate the microphone on Mixvibes 7.21 with the "Ext A" button on the BCD3000.
Thank you.