Setting up a Drop Down Menu for Digital Download

I am working with a client that needs to have a drop down menu for payment buttons so that when the options are changed it will properly correspond and only download that particular file. The system used is e-junkie. The codes that would be used for links are as follow below:

<a href="https://www.e-junkie.com/ecom/gb.php?c=cart&i=1257310&cl=207948&ejc=2" target="ej_ejc" class="ec_ejc_thkbx" onClick="javascript:return EJEJC_lc(this);"><img src="http://www.e-junkie.com/ej/ej_add_to_cart.gif" border="0" alt="Add to Cart"/></a>

<a href="https://www.e-junkie.com/ecom/gb.php?c=cart&i=1257314&cl=207948&ejc=2" target="ej_ejc" class="ec_ejc_thkbx" onClick="javascript:return EJEJC_lc(this);"><img src="http://www.e-junkie.com/ej/ej_add_to_cart.gif" border="0" alt="Add to Cart"/></a>

<a href="https://www.e-junkie.com/ecom/gb.php?c=cart&i=1257309&cl=207948&ejc=2" target="ej_ejc" class="ec_ejc_thkbx" onClick="javascript:return EJEJC_lc(this);"><img src="http://www.e-junkie.com/ej/ej_add_to_cart.gif" border="0" alt="Add to Cart"/></a>

If I am correct some basic HTML to create the drop down menus using the <form>, <option> and <select> tag will be the starting point. Also would need submit button so that when a specific option is choosen it will go the link for item choosen in drop down menu. in other words I would need to have the link for add-to-cart button change based on option that is choosen. Any help at figuring this out would be much appreciated.

The only other problem potentially is that I need the "add-to-cart" button to also function with view cart:

<a href="https://www.e-junkie.com/ecom/gb.php?c=cart&cl=207948&ejc=2" target="ej_ejc" class="ec_ejc_thkbx" onClick="javascript:return EJEJC_lc(this);"><img src="http://www.e-junkie.com/ej/ej_view_cart.gif" border="0" alt="View Cart"/></a>
<script language="javascript" type="text/javascript">
<!--
function EJEJC_lc(th) { return false; }
// -->
</script>
<script src='http://www.e-junkie.com/ecom/box.js' type='text/javascript'></script>

Edited October 10, 201312 yr by champ