Thanks for the help, what I am trying to do is to reveal the map just around a certain point...

A player needs to be able to 'see' a volcano for it to erupt. Because of the change in scale on the Sicily campaign map, it is very unlikely that a player will have units near MT Etna when it erupts, so the volcano effect is lost. Perhaps if I could use a script to reveal the volcano for the player (but not the rest of the map), the player would be able to see it erupting...