ReadOnly cannot receive any value

The following code works properly when I use a "text" type field as a target of the "editor.set" function, but when I change it to a "ReadOnly" field, it does nothing, even the alert box does not shows up.

I have also tried to use !this.get("TEXT_TYPE_FIELD_Z") to get a field value but it's not working, how can I get the input on a text field?
And how can I convert it to integer to multiply it?

    editor.on('onOpen', function () {
        $(document).bind('keyup', function (e) {
			if ( e.keyCode >= 0 ) {
					editor.set("TEXT_TYPE_FIELD_A", "If you can see this, is working");
					alert("It worked");
			}
		} );
	} );