How to copy some line and its textFormat from textField

the example of my problem is:

   I have 2 textFiled  there are:

                       1. myTextFied   ( to store the original text )

                       2. displayText     ( to show some line of  original text )

   I try this:

   myTextField.htmlText = '<B>THIS IS A TEXT LINE 1</B>\n' +

                                       '<I>THIS IS  A TEXT LINE 2</I>\n' +

                                       '<U>THIS IS  A TEXT LINE 3</U>';

      myTextField is  narrow  and I set myTextField.wordWrap =   true;

      So the result of myTextField display like this: 

                                                             THIS IS A TEXT

                                                             LINE 1

                                                            THIS IS A TEXT

                                                             LINE 2

                                                             THIS IS A TEXT

                                                             LINE 3

      and I use displayText to get  text of line 2 and line 3 from myTextField:

       so i try this:

                                             displayText.htmlText =  myTextField.getLineText(1);

                                             displayText.htmlText += myTextField.getLineText(2);

     but the result of  displayText  like this:

                                                              LINE 1 THIS IS A TEXT

       it not same the original textFormat.

        I want to make it to display like this

                                                             LINE 1

                                                             THIS IS A TEXT

                        How to find it out. Can you guy help me please!!!

  Thank you

and sorry about my English.