Hi Anderson, Thanks a lot for your reply. We are using an external set of IC maps. We want to compare week 0 to week 1 and 2 and week 2 to week 3 and 4. Thanks again, Alex ######################################################################## To unsubscribe from the FSL list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=FSL&A=1