You cannot create, in an AOI, a local tag of data-type MESSAGE.
When you want to use a message instruction in an AOI, the Message Control tag must be declared as an In/Out parameter, and therefore its elements cannot be addressed inside the AOI. So dynamically changing the message inside the AOI is a no-go.
A way round this is to have a bunch of message tags pre-configured, (and you can't create an array of MESSAGE tags).
As you call each AOI, you will have to specify which Messaqe tag the AOI will use as a parameter in the AOI instruction.