flash actionscript:

Hello...

I'm biulding a content management system.
I've got to the pioint where a user can type a link address into a text box and
the lick text into another box, click a button and have this populate
the "copy"
dynamic text box. Only trouble is, I can only put the new text either
at the end
of the text (which is pulled from a remote .txt file), or have it
replace all the text.

Is there a way to clik somewhere in amongst the text and have he new
text added just there?

All and any help much appreciated.
Best wishes
Tony

(fla file available if you need it...)