Here's one approach, though it is off slightly due to the difference in width between and x and an underscore character. Maybe you can fiddle with it and find a character that has the same width as the underscore. It looks like you also need to adjust how you compute the width property.
myTitle.text = "The ____ jumped over the ____ with a ____ in the ____";
var mystr:String = myTitle.text;
var myArr:Array = [];
myArr = mystr.split("____");
trace(myArr.length);
for(var h:Number = 0;h<myArr.length-1;h++)
{
var hTarg:hTClip = new hTClip();
addChild(hTarg);
var a : int = (myTitle.text as String).indexOf("____");
var b : Rectangle = myTitle.getCharBoundaries(a);
hTarg.x = myTitle.x + b.x
hTarg.y = myTitle.y + b.y
hTarg.width = (b.width);
hTarg.height = b.height;
// take the current set of underscores out
var myPattern:RegExp = /____/;
myTitle.text = String(myTitle.text).replace(myPattern, "xxxx");
}
// put all the underscores back in
var myPattern2:RegExp = /xxxx/g;
myTitle.text = String(myTitle.text).replace(myPattern2, "____");
Edit: Obviously, Peter's solution is much better. He knew of what I was wishing for... the start index parameter for the indexOf method.
I was writing it for a while and didn't notice Ned's answer. To be fair, he deserves correct.
