<form name=”PayBox” id=”PayBox”>
<input type=”hidden” name=”remail” value=”gateway account email”>
<input type=”hidden” name=”sendmail” value=”buyer email”>
<input type=”hidden” name=”amount” value=”$10″>
<button onclick=”submitPayBox()” id=”pay”></button>
</form>

need to add, the functionality of the Place Order default button at checkout page, that validates the checkout form data submitted by user (like First Name, Billing Address, etc…) and grabs basic values submitted, like the total amount of the order and billing email (which is easy to grab with woocommerce API), but the question is how do I add to my Buy Now button, the functionality to validate the forms fields and grab the information from the checkout form in order to load that data to my Payment Gateway PopUp. Well what i all do is when the user, clicks on my gateway it will hide the default Place Order button and replace it with my Buy Now button, so thats where i all need to have the same functionality of the Place Order button on mine.

So i all appreciate the help, thanx a lot.

Replicating this from scratch would be beyond my knowledge, but one thing I could suggest is looking at the checkout templates that already exist in WooCommerce or one of our free payment methods like PayPal Express that uses a pop-up or Stripe when you enable Stripe Checkout (another modal/pop-up).

There are surely examples there you could glean some insight from on how our developers have done something very similar.

Also, hopefully, some of my much brighter colleagues or other open source friends can add a better answer here. ??