I'm going to take a stab in the dark on this one since no one else has responded yet.
Getting a "through a reference with static type" error means what you are trying to access is a Static variable/function. To access these you need to use the class name like
ActionScript Code:
public class Enemy extends Sprite {
static public function changeCostume(newCostume:Sprite):void
{
//someCode
}
}
//To access this from outside I would use
Enemy.changeCostume(newcostume);
//Not
myEnemy.changeCostume(newCostume);
So try using:
ITextInput.setSelection(int, int);
I've never used ITextInput but this looks like it would be the issue.