The method usually suggested in Word when you have a few frequently used "words" that violate the sensibilities of the automatic capitalization correction depends on knowing which of the "replacers" runs first.
The utility that changes capitalizations generally runs "on the keystroke" as you type. It will change your capitalization, but the "Autocorrect as you type" generally follows it by a few milliseconds.
If you put the capitalization that the "corrector" will use into the Autocorrect dictionary as a misspelling, with the original capitalization that you'd type as the "correct spelling," every time the "capitalizer" changes what you type, the "autocorrector" will put it back.
Without knowing how to automatically correct the incorrect correction made by the "first corrector" via "the other corrector," correspondence with the company that called themselves BaC was a real hassle, since every time you typed their common name it changed to Bac or to BAC, both of which were wrong.
There are several other "company names" that offer similar challenges, and of course acronyms and initializations offer a wealth of marvelous examples.