Include results of a Paypal button generator in post without copy/paste

I own a locally exclusive trade form for people to sell items to others locally. I want to have an option to include a Paypal "Buy Now" button in new posts but I'm stuck at how to include the button in a new post without having the user manually copy/past the HTML. I have made a simple Paypal button generator with a checkbox and jQuery to display form fields if checkbox is checked. Here it is on jsfiddle

HTML

<form>
<input type="checkbox" id="checkme" /> Add a "Buy Now" Paypal button 
</form>
<div id="extra">
<form action="includes/paypal_button.php" method="post">
Paypal account email: <input type="text" name="email" /><br />
Short item description: <input type="text" name="item" /><br />
Price for item (all amounts are in USD): <input type="text" name="amount" /><br />
Tax amout: <input type="text" name="tax" /><br />
Shipping and handling: <input type="text" name="shipping" />
<input type=submit value="Create Paypal button!">
</form>
</div>

jQuery

<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.3/jquery.js"></script>
<script type="text/javascript">
    $(document).ready(function(){
        
        //Hide div w/id extra
       $("#extra").css("display","none");
        // Add onclick handler to checkbox w/id checkme
       $("#checkme").click(function(){
        
        // If checked
        if ($("#checkme").is(":checked"))
        {
            //show the hidden div
            $("#extra").show("fast");
        }
        else
        {      
            //otherwise, hide it 
            $("#extra").hide("fast");
        }
      });
    
    });
</script>

The controller form is in a separate php script, paypal_button.php

HTML

<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
<input type="hidden" name="cmd" value="_xclick">
<input type="hidden" name="business" value="<?php echo htmlspecialchars(($_POST["email"]))?>" >  
<input type="hidden" name="lc" value="US">
<input type="hidden" name="item_name" value="<?php echo htmlspecialchars(($_POST["item"]))?>">
<input type="hidden" name="amount" value="<?php echo htmlspecialchars(($_POST["amount"]))?>">
<input type="hidden" name="currency_code&qu开发者_Python百科ot; value="USD">
<input type="hidden" name="button_subtype" value="services">
<input type="hidden" name="tax_rate" value="<?php echo htmlspecialchars(($_POST["tax"]))?>">
<input type="hidden" name="shipping" value="<?php echo htmlspecialchars(($_POST["shipping"]))?>">
<input type="hidden" name="bn" value="PP-BuyNowBF:btn_buynowCC_LG.gif:NonHosted">
<input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_buynowCC_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
<img alt="" border="0" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" width="1" height="1">
</form>

So should I include the controller(the button to print) in a php if statement that will print the button in new form posts? It would be highly appreciative if someone could point me in the right direction.

Thanks in advance