Why is this sub A a’ by a.alt; not working?

This

sub A a’ by a.alt;

is not working. It keeps giving me an error. It works (not the way I want) if I remove the apostrophe.

You need to use a strait tick mark, you have a curly quote. The feature edit view sometimes switches itself to autocorrect mode. Right click it and disable everything in the Substitution group.

I will try that. Thanks!