Change the border of a shape

[MTTM]

Hi 2 u all!
I am trying to make an application that let's u draw some figures. So for so good. I am stuck in finding a solution in how to change a shapes border thickness after i added to the stage.

var _testMC:MovieClip = new MovieClip();

_testMC.graphics.lineStyle(3, 0x006699, 1);
_testMC.graphics.beginFill(0xFF0000);
m_testMCc.graphics.drawRect(0, 0, 100, 80);
_testMC.graphics.endFill();
_testMC.x = 80;
_testMC.y = 60;
addChild(mc);
_testMC.addEventListener(MouseEvent.CLICK, onClick);

function _testMC(event:MouseEvent)
{
// i dont't have any idea how to modify the the lineStyle thickness
// i've read something with copying tha graphics ...but i didn't like that way
// any ideas ??
}

Thanks! :P