Updating cart instead of Form submit

This allows to update my cart, but returns back to the top of the page.

I don;t want it to return back on top, so how can i do it using Javascript ?

Below is my code for the form.

<form class=”product_form” enctype=”multipart/form-data” action=”#” method=”post” name=”product_<?php echo wpsc_the_product_id(); ?>” id=”product_<?php echo wpsc_the_product_id(); ?>”>
<input type=”hidden” value=”add_to_cart” name=”wpsc_ajax_action”/>
<input type=”hidden” value=”<?php echo wpsc_the_product_id(); ?>” name=”product_id”/>
<input type=”hidden” name=”wpsc_quantity_update” value=”500″>
<input type=”submit” name=”500″ class=”image-button500 wpsc_buy_button” id=”product_<?php echo wpsc_the_product_id(); ?>_submit_button” value=”/>
</form>

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