This is an updated version of Hammersbald's AfterCast, which is an update of Iriel's AfterCast. What I fixed is the editbox problems that came with the 3.3.5 update and the Unexpected Event spam.

Original version 1.1-20000 of this Addon can be found here:
http://www.wowinterface.com/downloads/info4167-AfterCast.html

Fan's Update can be found here:
http://www.wowinterface.com/downloads/info14404-AfterCastFansUpdate.html

Original description below:
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AfterCast - Perform action after a cast
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This is a fairly simple addon for performing actions based on the success or failure of a cast. Usage is as follows

/aftercast /smile
/aftercast +fail /cry
/cast Frostbolt(Rank 2)

If the spell succeeds then you'll smile, if it fails, then you'll cry. If it is interrupted then nothing will happen. You can also use the shorter command,

/ac +start /p Casting Resurrection...
/ac +done /p Resurrection Done!
/cast Resurrection

Events you can use are:

+done At the end of successful casting (Default if no event given)
+fail If the spell fails
+interrupt If the spell is interrupted
+start When spell starts casting (Fires before done for instant spells)

Aftercasts apply to the next spell which occurs, and then is reset, you can set up one of each event before each cast.

These functions can also be gotten at via lua functions:

AfterCast(doneAction, failAction);
Shortcut to set up the 2 most common actions, either can be nil.

AfterCastOn(event, action)
Set up a specific action (use without the +, so "done", "fail", etc)

AfterCastReason([clearFlag])
Return the stop reason ("done"/"interrupt"/"fail") for the last cast (nil if none have stopped since the last clear).. if clearFlag is present and true then resets status after return.