Show un-selected options from multiple select field in a separate field

I have a couple fields that are all multiple selects, that I want to consolidate to one field that tells me what wasn’t chosen.

For Example, I have 3 fields called VIDEO, AUDIO, GRAPHICS all with multiple options to select. I want to create a field that combines them all with the unselected options.

If VIDEO has the options: Master, Web, DCP and I select only Master and DCP
If AUDIO has: Stereo, 5.1, Stems and I select only Stereo, 5.1
If GRAPHICS has: poster, stills and I select only poster
Then I want one field Called Missing that outputs the missing options: Web, Stems, stills

Thank you.