Wordpress functions in external js file

Hello, i'm creating a wordpress template but i ran into a problem... i've created a contact page... with a contact form

this is the form

<form method="post" name="contatti" id="contatti" action="<?php bloginfo('template_url'); ?>/inviaemail.php"> 
	<div id="contact_area">
		<h2>Contattaci direttamente via email</h2> 
	
		<input type="text" name="name" id="name" class="form" value="Nome*" />
		
		<input type="text" name="email" id="email" class="form" value="e-Mail*" /> 
		
		<input type="text" name="sito" id="sito" class="form" value="Sito Web" /> 
		
		<textarea name="message" id="testo" class="form" rows="12" cols="" >Testo*</textarea>
		
		<div> 
			<input type="submit" name="submit" id="invia" value="Invia"/>
			<img src="<?php bloginfo('template_url'); ?>/images/load.gif" alt="load" id="load_img" />
			<span id="result"></span>
		</div>
	</div> 
</form> 

PHP:

This is a part of the ajax validation script from a js file into the theme template...

else {
			$('#load_img').fadeIn();
			$.ajax({
				type: 'post',
				url: 'inviaemail.php',

Code (markup):

as you see, url : 'inviaemail.php' , is the file that send the email, but currently it try to load this file from the wordpress root, i need to load this file from the theme folder... wordpress got a php function to do this

<?php bloginfo('template_directory'); ?>

PHP:

how can i make the js file to load inviaemail.php from the theme folder ?

sorry for bad english...