<form target="paypal" action="https://www.paypal.com/cgi-bin/webscr" method="post" >
<input type="hidden" name="cmd" value="_cart">
<input type="hidden" name="business" value="Your@email.com">
<input type="hidden" name="lc" value="US">
<input type="hidden" name="item_name" value="Shopping Cart">
<input type="hidden" name="button_subtype" value="products">
<input type="hidden" name="no_note" value="0">
<input type="hidden" name="no_shipping" value="0">
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="add" value="1">
<input type="hidden" name="bn" value="PP-ShopCartBF:btn_cart_LG.gif:NonHosted">
<input type="hidden" name="on0" value="Sizes"><select name="os0">
    <option value="Small">Small $5.00 USD</option>
    <option value="Med">Med $7.00 USD</option>
    <option value="Larg">Larg $10.00 USD</option>
    <option value="Super Size">Super Size $15.00 USD</option>
</select>
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="option_select0" value="Small">
<input type="hidden" name="option_amount0" value="5.00">
<input type="hidden" name="option_select1" value="Med">
<input type="hidden" name="option_amount1" value="7.00">
<input type="hidden" name="option_select2" value="Larg">
<input type="hidden" name="option_amount2" value="10.00">
<input type="hidden" name="option_select3" value="Super Size">
<input type="hidden" name="option_amount3" value="15.00">
<input type="hidden" name="option_index" value="0">
<input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_cart_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>