I have data in columns A and B. Column A is employee's names. Column B is
trainings they have attended. The person's name is duplicated several times
in A as they have attended multiple trainings.

I need a filter (or a code) that will list all staff who hasn't attended a
specific training.

It isn't as simple as filtering Column B to all rows that < the specific
training because the person's names are duplicated in A because they have
attended other trainings. I don't even know who to work this clearly???