Apply an embedded font to TextField created via script?

I have a movie that uses imported fonts:

In want to create TextFields via AS3 and use this improted font on it:

var tf:TextField = new TextField();

var format: TextFormat = new TextFormat();
format.font = "$ColdDefaultFont";
tf.text = "Some text";
tf.setTextFormat(format);
			
addChild(tf)

However the font is never displayed (just shows as squares). If i manually add a TextField to the stage and set it's character font to use this embedded font it works fine.

So what am I doing wrong here?

Thanks