Cannot apply a promocode on Start Over only with links

[trinidadhost]

I am using WHMCS 5.1.2. I am also using the boxes template in my order forms.

 

1. Order a package: http://www.trinidadhost.com/cart.php?a=add&pid=1'>http://www.trinidadhost.com/cart.php?a=add&pid=1&promocode=onemonthstarter

2. Add hosting plan to the cart (Add to Cart) button

3. On the page with the (Checkout >>) button there is a (<< Start Over) button

4. If the user chose to Start Over, then it goes back to a choice of my two hosting packages that wasn't shown up to this point. It also clears the data that was tracked so the cart is empty.

onclick="window.location='cart.php?a=startover'"

but I can't figure out how to add my promocode back to this because it switched from a link to a choice of radio buttons

 

I tried

onclick="window.location='cart.php?a=startover[color=#ff0000][b]&promocode=onemonthstarter[/b][/color]'"

but that didn't work

 

I also changed this link to go back to my index.php page instead, but I can't take advantage of the clear option so I end up with two choices in my cart because the original wasn't cleared.

 

So I need to know how to auto apply my promo code when I start over or how to clear my cart if I go back to my index.php page.

 

One note: if the customer uses the exact same domain name the second time, then I won't get duplicates, but if they put in another name, the start over doesn't work when I send them back to http://www.trinidadhost.com/index.php.'>http://www.trinidadhost.com/index.php.

 

Thanks for any help or ideas

 

TrinidadHost

http://www.trinidadhost.com