Moving to next frame based on 1 letter typed in a text field

Hello, I have a text field that will change display based on what is typed in the field, very similar to a drop-down menu.

What I need to know, is how can I have it navigate to the next frame if there is no action other than typing the correct letter in the field other than onChanged? Here’s my code;

keyword_txt.addEventListener(Event.CHANGE, textChanged);

function textChanged(e:Event)

{

            var a = keyword_txt.text;
            {
                            if (a == "D")
                            {
                                            gotoAndPlay("rbms_04-2");
                            }
                            else if (a != "D")
                            {
                                            keyword_txt.textColor = 0xFF0000;
                                            incorrect_mc.wrong_txt.text = "The correct first letter of the Diamond keyword is D. Please type a D in this field to continue.";
                                            }}

}