payment/distribution model contract/fee style

[new_asdf]

hi,

i got an app which should be for free to download but the service should be payed. it should go contract style (every month a fee should be payed).

for example: a game is downloaded for free with some free levels but after each month you can buy new levels.

is such a payment/distribution model possible with current app store?

if not what is the alternative? offer a normal webpage, which is used by browser? unfortunately i got a finished flash app usable through browser but safari does not offer flash player, so this application cannot be used

thanks for the info.