You should be able to update your 2017 USB with the new 2018 files and continue to run it from the external drive.
_________________________
John

#1-Win10Pro-64,8GB,7200RPM
#2-Win10Pro-64,16GB, 7200RPM
#3-Win7Pro-64,8GB,7200RPM
H/W: Onboard audio, Casio Kbds
S/W: BB/RB2017/Sonar/Reaper/Studio One/Samplitude/Notion/Finale/Noteworthy/NI Komplete/Halion/Garritan/IK
Web: http://www.sus4chord.com