Yes, you need to refresh it first before modifying, because the canned ICR points to the C drive. I've spent many hours modifying ICRs without refreshing first that I had to redo. I usually save the original ICR off somewhere else if no one is running the ICR routinely. Then I make all my changes in the ICR (not the one with my user ID attached to it). You can run as needed from the macola menu to test your work. When it's done, save it somewhere in case someone overwrites by accident or a macola update overwrites your version. Then, all your users have the same report instead of changing the report for every user who uses it.
If others use the report I want to modify, I edit it under my user ID attached to the report until I get it right, then save the orginal, copy over my edited version to the default ICR report name, etc.