If the XLL+ Function Wizard finds more than one copy of a function in a single source file, this warning is shown. If you choose to continue, the Wizard will still work, but you will only be able to edit the first copy of the function.
Note: You may have a legitimate reason for having two copies of the same function in a file. Indeed, you may have used a preprocessor instruction to exclude one of the copies. In this case, you must either put up with the warning and edit only the first copy of the function, or you should move the excluded code to a different source file.