Variables can be used to define a portion of a UNC path as shown above.  This single app will run NWADMIN from each users local server without having to define a different application for each server from which the application is run. 

These variables can based upon criteria such as IP address,  IPX network, group membership or the users' OU.

The Drives/Ports Tab of the application properties is one area where the power of the variable can be well demonstrated.  The app shown above could be used without modification for many users across many physical locations who user many different servers and print to many different printers.

The servers to which drives are mapped and the queues to which ports are captured can be specific servers or queues. They can also point to servers based upon a local environment variable. In the example above, one drive letter is mapped to a central corporate server, possibly across a WAN, which contains central data. A second drive letter is mapped based upon an environment variable which points to a generic application server which can vary from user to user based upon where the workstation is physically located.

The same principle could be applied to print queues. An environment variable containing the name of the default print queue for a given user logging into a certain workstation could be set. Therefore wherever and whoever ran the application, it would capture to a local printer and run the application from a local server while connecting to a central corporate server for data.

Variables can also make fault tolerance much simpler.  I frequently create a single application object that will remap users' network drives based upon the %failapps% variable for all network based applications.  If user's application server becomes unavailable and they try to run the ZEN APP, it will run the fail-over application which remaps the user to a working server.  One minor drawback to this is the first time a user clicks on the application, it will appear to do nothing when it actually remaps the user to a working server.  The user will need to click on the application for it to successfully run.  Optionally a message can be presented with the fail-over app such as "Network Error Corrected - Please Try Again."  This single app can be used by all user's regardless of the servers they use, which can significantly reduce network administration costs.