Hi there Ken,
There's no easy way to do it. But there is a bit of a 'hack' that will get the job done.
And yes, for those of you wondering, this method will let you skip any mission you want, but fair ...
WARNING: Using this method to skip missions you haven't beaten yourself is cheating. If that's your bag and is what you need to do to enjoy the game, then don't let us stop you. But we feel that the most enjoyable way to play through the game is to play each mission in order, and to overcome the challenges in the game yourself!
That said, if you absolutely want to pass one or more missions, here's what you need to do:
(Be sure to follow these instructions carefully. If you go changing random things in your registry, you can cause software to stop working correctly. If you follow these instructions exactly you'll be fine, but still, USE AT YOUR OWN RISK.)
-Click Start-->Run, type 'regedit' (no quotes) and press enter.
-Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Shrapnel Games\Land of Legends\Profiles\<ProfileName>\Land of Legends\Standard (or Legendary)
-Right-click on the mission you want the game to think you've finished and select 'Modify'.
-Change 'False' to 'True' and then click 'OK'
-Repeat the last 2 steps for each mission you want to pass.
When you restart Land of Legends, it will think you've passed the missions that you changed in the registry.
I hope this helps!
-Hiro_Antagonist