I work for Minitab and I checked with our tech support team about your question. Unfortunately, there isn't a way to exclude outliers yet in Minitab, but I've submitted this request to our feedback team on your behalf. (Feel free to submit other feedback you have about the software directly to the feedback@minitab.com email address.)
If you'd still like to remove the outliers from your data set, look at the table of unusual observations, then subset based on the row number that the unusual observation is located in.
If you have further questions, don't hesitate to contact our tech support team at http://www.minitab.com/support/