[jQuery] Masked Input Field

[jQuery] Masked Input Field

Im asking alot of questions today, sorry.
Trying to use this.
<a href="http://digitalbush.com/projects/masked-input-plugin">http://digitalbush.com/projects/masked-input-plugin</a>
It is an awesome plugin by the way!
I have one field called creditcard (guess what goes in there)
And another select called credtcardType (amex, visa, mc, discover)
I want to put in the spaces like this 9999 9999 9999 9999.
But for Amex I want 9999 999999 99999.
Ultimately, I want to submit to the server without spaces. (Maybe a hidden form field)
How should I achieve this?
Posibility #1: Have different fields for each credit card type and show/hide them based on the ccType select.
Possibility #2: onChange of the select, change the class of the input and then re-apply the mask with an if statement which reads the class and applies the correct mask.
Totally unsure how to do this.
Possibility #3: Pray
Any help is greatly appreciated.
Glen