That worked perfectly! So this is the code that worked:
<?php
return ' <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Appointment Scheduler</title>
</head>
<body>
<div>
<iframe src="http://www.MYWEBSITE.com/core/components/MYSCRIPT/index.php" scrolling="yes" width="100%" height="600">
</iframe></div>
</body>
</html>';
?>
Would have never even gotten close without you, this is awesome. Now that I can run external PHP scripts directly into MODx, this give me lots of tools that might not be available via add-on.
I just have one easy question now. Do I have to install these programs directly in the core/components/MYPROGRAM folder or can I install them outside of the MODx folders but then call them in via the iFrame file? My only concern with having them directly inside MODx is that when I add the Javascript to the front end pages of the website, the script location will shows which perhaps makes MODx less secure. Maybe I am wrong I don't know. This would be the Javascript code I add to the front end pages:
<link href="http://www.MYWEBSITE.com/core/components/MYSCRIPT/index.php?controller=Front&action=css&cid=1" type="text/css" rel="stylesheet" />
<link href="http://www.MYWEBSITE.com/core/components/MYSCRIPT/index.php?controller=Front&action=loadCss&cid=1" type="text/css" rel="stylesheet" />
<script type="text/javascript" src="http://www.MYWEBSITE.com/core/components/MYSCRIPT/index.php?controller=Front&action=loadJs"></script>
Would this be a security concern?