ActionScript 3.0 :: SelectionBeginIndex Not Taking Into Account Linebreaks?

I've got a TextArea with some text in it. Sometimes there are linebreaks.

I'm using SelectionBeginIndex and SelectionEndIndex, along with substring() to get the current selection.

The only problem I'm running into is that if that selection includes any line breaks, it doesn't understand.

For example, if the text was:

Code:
This is my first line of text.

ABCDEF
Let's say I selected from the first letter all the way to, and including, B.

The output of the substring() with the begin and end selection, because of the linebreaks, would be:

Code:
This is my first line of text.ABCD

Here's the AS Code I used to illustrate the problem.

ActionScript Code:
checkButton.addEventListener(MouseEvent.CLICK, checkSelection);
myText.alwaysShowSelection = true;
myText.textField.alwaysShowSelection = true;

[Code].....

How can I capture those linebreaks? htmltext isn't an option, because there's no selectionBeginIndex and selectionEndIndex for htmltext...