MACROMEDIA FLASH MX 2004-ACTIONSCRIPT LANGUAGE Reference page 730

set("name", "Jakob");
trace(name);
The following code loops three times and creates three new variables, called , ,
caption0 caption1
and :
caption2
for (var i = 0; i<3; i++) {
set("caption"+i, "this is caption "+i);
}
trace(caption0);
trace(caption1);
trace(caption2);
See also
var, call()
730 Chapter 2: ActionScript Language Reference