Help adding a popup Calendar field to my php reservation form

I’m trying to build a reservation form for a client:

I would like to implement a dynamic date selector, which adds a popup Calendar field to the form when a user wants to enter a departure/arrival date. It would look exactly like this:

I’m not a developer, so I’m a little lost when it comes to php and javascript. Any help would be much appreciated.

Here’s the php code for the form I want the calender popup to apply to:

<input type="text" name="Date_of_Outgoing_Flight" value="<?php print HtmlSpecialChars( $HTTP_POST_VARS[ "Date_of_Outgoing_Flight" ] ); ?>" class='text_box'>

And some how I have to apply this javascript, which should enter the date info from the calender in the desired place in my form above:

This is my section:

<script type="text/javascript" src="calendarDateInput.js">
* Jason's Date Input Calendar- By Jason Moon [](
* Script featured on and available at [](
* Keep this notice intact for use.

And this goes some where in the body…but I can’t figure out how to apply it.

<script>DateInput('orderdate', true, 'DD-MON-YYYY')</script>

I’ve attached my php form and the external .js file for the popup calender.