Hi,
The trigger onHikashopBeforeDisplayView has a variable &$view
To get the current controller, you can use $view->ctrl
To get the current task, you can use $view->getLayout()
To get the current step, you can use $view->step
To get the current position, you can use $view->module_position
To get the options of the current view, you can use $view->options
So basically, you can have such code so that you skip your code if you're not in the checkout:
if($view->ctrl != 'checkout' || $view->getLayout() != 'show') return;
Supposing that you add your input fields in the address view form, you can use the onAfterAddressCreate and the onAfterAddressUpdate triggers to check the data in $_POST.
We use something similar with the recaptcha plugin which adds the catpcha in the registration form of the "login" view with the onHikashopBeforeDisplayView trigger and then checks the captcha in the onUserBeforeSave trigger called before the new user is being created.
www.hikashop.com/support/documentation/7...-with-recaptcha.html