Calvin Johnston Joins Excell & Nissco Buying Groups Calvin Johnston Joins Excell & Nissco Buying Groups Calvin Johnston Joins Excell & Nissco Buying Groups The Excell and Nissco buying groups welcome industry veteran, Calvin Johnston as Vice President of Business Development. Calvin Johnston Joins Excell & Nissco Buying GroupsStrata GPO2023-04-17T10:35:27-06:00