Platform Hittest

Ok im making a platform game first time since I ever started Flash programming…

Anyways I want the Character to not fall through the platform or jump form below a platform and go through it.

The Code

onClipEvent (enterFrame) {
	if (hitTest(_root.hero)) {
		_root.hero._y = this._y-68;
		_root.hero.platform = "on";
	}
}

Thats the code that im using came from a tut that im doing but found that the tut wasent all that great so started folli around with the code.

Also with that code if i make the platform bigger it doesent work and it takes a long time in order to get the platform wokring.

I was thikin of adding alot of diffrent platform but dont want to keep changin the code.

Anyone Got Some Help?