在网格模式下单击产品视图页面按钮时需要打开两个URL吗?

Need to Open Two URL while clicking product view page button in grid mode, Basically its a coupon site. In Grid mode when clicking the product view page button. It has to open product page url & coupon site url. Am facing an error. When clicking the button, It opens the product page of last product in the grid view.

The Code i used is

<p><button type="button" title="<?php echo $buttonTitle ?>" id="product-addtocart-button" class="button btn-cart" 
                        onclick="openWindow()"><span><span><?php echo $_product->getCouponCodeUse(); ?></span></span></button></p>                                          
                        <script type="text/javascript">
function openWindow() {
var popup = window.open("<?php echo $_product->getCouponUrlValue() ?>","_self");
            window.open("<?php echo $_product->getProductUrl() ?>","window1");
            
}</script>

Help me out in this issue

Thanks in advance.

</div>

Here is a working fiddle example that opens 2 windows on the same click event.

jsfiddle example

http://jsfiddle.net/mdamia/mkcvmbhj/9/