Word index and definition entry trick
In word we can use an INDEX entry to define the TLA (Three or more Letter Acronym) AND The expanded acronym definition. The syntax must be EXACT (XML entries I suspect) and the markers can be ID'd throughout the document if needed looking for the TLA and replacing it with TLA { XE "TLA:Three Letter Acronym" } (Where the grey text is a field ALT+(F9))