Thanks so much Andrew; that worked. A bit of backstory: I'd become frustrated by the limited icons available to create QAT buttons, so I found a web site that offered the codes for many other icons (
Office Excel Ribbon imageMso icons gallery page 01). It said it was for Word 2016, but it did appear in my Word 2007 QAT, so I thought I was good to go. When I took your advice, I changed the icon to one of the ones on offer in Word, and now the macro runs fine. I guess I should update Word. . . .