Excluding Subjects in Second-Level Covariates

Hello, 

I saw that this was a thread a couple of years ago and wanted to see if the protocol has changed. I would like to exclude two participants from a second-level analysis after they had been preprocessed. How exactly should I go about doing so? 

I tried entering 'NaN' in place of a number, but CONN could not recognize the string when I did this.

Thank you.