JQuery :: Validate - Check Zip And Return City Into Another Input

I use the Validation plugin [URL] and do like this:
frmzip: {
required: true,
digits: true,
remote: zip.php,
},

I have two fields; zip and city, I validate zip with remote and it checks against a list if the zip is valid, but i want it too:
Check if the zip is valid
Return true if it is valid and return the city of the zip and paste it in the city-input...
Of course I have a database/array/list with all zip and city's.