AS 2> Dynamically loaded text to resize container mc

Hi there, ive been all day coding and going through search result pages with no luck. Basically, i want to build my own scrollbar from cero. Its all going good, but to make the scrolling thingy i need a mask, a container mc which contains (obviously!) a dynamic text which is loaded externally.
This is the problem: who do I set the mc to the same height from the dynamic text once is loaded?
so far, i have accomplished that indeed the mc resizes to the dynamic text height, though all the text scales as well… who do i do it without the text itself scaling?

These guys had the same questions though i could find a proper andwer in the posts:

My last effort contained this script on the containcer mc:

onClipEvent(load) {
this._yscale = this.instance_text.textHeight;
}