Interesting spell, need help!

Interesting spell, need help!

If i have buff name "spell" and enemy do spell on you, and enemie's spell dmg ==300, my buff will remove from game, and enemy will lose 1500 ower 5 seconds.

Events
Unit - A Unit Starts the Effect Of an Ability
Conditions
Ability Being Cast Equal to xxx
Target Unit of Ability Being Cast has buff Spell Equal to True
Actions
Set loc = Position of Triggering Unit
Unit - Create 1 Dummy at loc
Custom Script - call RemoveLocation( udg_loc )
Unit - Add (dummy) to Last Created Unit
Order Last Created Unit to cast (dummy) on Target Unit of Ability Being Cast
Unit - Add a 1 second Expiration Timer to Last Created Unit
Unit - Remove Spell ( buff ) from Target Unit Of Ability Being Cast