How to update a package using puppet and a .deb file

I am trying to figure out the proper way to update/upgrade a deb package using puppet from a local source deb file. My current config looks like this...

class adobe-air-2-0-4 {

  file { "/opt/air-debs":
    ensure => directory
  }

  file { "/opt/air-debs/adobeair-2.0.4.deb":
    owner   => root,
    group   => root,
    mode    => 644,
    ensure  => present,
    source  => "puppet://puppet/adobe-air-2-0-4/adobeair-2.0.4.deb"
  }

  package { "adobeair":
    provider => dpkg,
    ensure => installed,
    source => "/opt/air-debs/adobeair-2.0.4.deb"
  }

}

I first copy the deb file down to the client machine and then use 'package' with the provider set to 'dpkg'. This works and I get the correct version installed.

My question is what is the proper way to update this package in the future. Can I simply change out the source file and puppet will know that it's a different version and update this package? How does puppet determine what version of a package it has installed versus the version of the source deb file?

I am pretty new to puppet, so if you have an suggestions for improvements to my existing config they are very much appreciated.

I also posted this question on the puppet users group and this was a response that I got back.

If you add ensure latest it will check the source file against the currently installed package and install the new one if it is latest. I'm still not sure how you would roll back to an older version, but this seems to solve my problem for now.

package { "puppet-dashboard":
 provider => dpkg,
 ensure   => latest,
 source   => "/tmp/puppet-dashboard_1.0.4rc2-1_all.deb"
}

Here is a link to the puppet user group post... http://groups.google.com/group/puppet-users/browse_thread/thread/53f5e7119012fb3e/59e8596701fcaf3f