Encrypting using "Cryptography.HMACSHA1", how to decrypt (VBA)
HMAC is a message authentication code (MAC). MACs produce "tags" that can can be used to prevent a message from being tampered with (sort of like a digital signature). There's no way to "decrypt" an HMAC tag to get back the original message, so it sounds like HMAC is not what you're looking for.

I would suggest using AES-GCM instead, since it's designed to be used for encryption. I'm not sure how to use AES-GCM from VBA: I suggest asking that on StackOverflow (that question would be off-topic here).