Autocorrect can do that. Go to the FILE tab of the ribbon bar, then Options, then Proofing (I think. I have 2013). Click on the "Autocorrect Options" button. In the section for "Replace text as you type" (as long as it's checked), you can put the shorthand text in the "Replace" blank, and SPEAK SELECTED TEXT in the "With" blank. Click the "Add" button, and it's done.
CAREFULLY choose the shorthand text, though. Autocorrect is very literal. It'll do the replace even in the middle of words if you use a plain text shorthand. I recommend putting some kind of special character in there. For example, I use brackets, like with the UBB code we use in these forums. For example, I might use [mer] to have Autocorrect make it "The Merriam-Webster Online Dictionary".
Because I don't see myself ever using UBB code in MS Word