Hi,
You could use script in the mouseEnter event:
this.font.size = "16pt";
This may also change the font size of the caption (from memory), so you might need this:
this.font.size = "16pt";
this.cpation.font.size = "10pt";
Then on mouseExit event:
this.font.size = "10pt";
Hope that helps,
Niall