How can I ask for User confirmation in a Binder validation?

Let’s say I have the following Binder validation on the Bean BankAccount:

binder.withValidator(bankAccount ->
         return false;
    return confirmCustomerWillAcceptTransactionFee();
}, "Cannot withdraw money");

How can I confirm that the customer will accept the fee before proceeding? The only dialogs I can see that return user feedback have a callback method therefore I can’t seem to figure out how to do this in a Binder?

For a form you can hook into the save button, but for the Grid Editor this becomes much more important as I cannot see a mechanism which allows me to confirm the user is ok with an extra in the above example…

How about you add a checkbox and have the validator look at whether it is checked?

The problem with that I may or may not need to apply the transaction fee depending on the specifics of that transaction. In other words the confirmation is only required in some situations and not all situations.