[Embed(systemFont="Helvetica", fonName="Helv", 
	   mimetype="application/x-font", unicodeRange="U+002C-U+0039, U+0041-U+005A]")]
var helvetica:Class;
Font.registerFont(helvetica);


U+0020-U+0040, /* Punctuation, Numbers and Symbols */
U+0041-U+005A, /* Upper-Case A-Z */
U+005B-U+0060, /* Punctuation and Symbols */
U+0061-U+007A, /* Lower-Case a-z */
U+007B-U+007E; /* Punctuation and Symbols */

Unicode font subsets

ActionScript 3