Payment Alert Popup - javascript code hack

[DogTags]

I'd like to have an Alert popup when the customer clicks any of the payment radio buttons.

Basically, I want them to confirm that they really want this or that payment option.

I've had a number of customers at first choose credit card, then their card gets declined, then they come back and select check/money order to complete their order, but then they'll write in saying that they had paid with their credit card. Yes, it really happens.

So, I think having an Alert popup to confirm their payment choice would be a nice feature.

The Alert should contain the name of the payment choice, obviously.

Would anyone know how to hack this Alert popup in?

Many thanks