NoSparks, thank you for asking. I actually found the problem in between: the character I was looking to replace was "," (comma). The problem was coming from the fact that I ad moved to a new computer, and localization settings were slightly different.. On this new one byd efault "," was the decimal separator. Thus I guess it was not managed as a "normal" character by Excel. After changing the decimal separator to "." in my settings, the macro restarted to work fine.