How to redirect to the required page from the WHMCS cart?

Question

htaccess

It is necessary to redirect immediately after placing the goods in the basket.
Tried Redirect 301 /cart.php?a=add&pid=1 /custom-pageand

RewriteEngine On
RewriteRule ^/custom-page([/]*)$ ./cart.php?a=add&pid=1 [L,NC]

However, the redirect did not happen.

Answer 1

I won't answer even already I'm tired.
But I'll give you how to ask the right question
1. a redirect from a get is not part of the url
2. a redirect to a get is harder to find, so I'll help
Pay attention to the screen before ?
well, a bonus
https://donatstudios.com/RewriteRule_Generator