In the body of the message, if you put \n[number], with [number] as the database number of the actor whose name you want to print, it'll automatically print their name regardless of name changes.
For instance, let's say Arshes is actor 1 in the database. You enter this into the Show Text box:
Hello, \n[1], isn't it a fine day?
In game, it will be displayed like this:
Hello, Arshes, isn't it a fine day?
If you then change Arshes' name to Fred, the NPC's message will change as well:
Hello, Fred, isn't it a fine day?
That help?
Looks like FireRaven beat me to it, though.