Ability need resoruces?

[Kerotan]

In my map a building has an ability which i want too use lumber too beable too cast it, at the minute ive got the triggers working for the ability (too fire missles at distaces if your wondering) but i want it too use 50 wood, how can i do this? also too make sure it checks too see if you have enough and if you dont an error comes saying you dont have enough resoruces..

 

[Daminon]

Building Ability
Events
Unit - A unit Begins casting an ability
Conditions
Actions
If (All Conditions are True) then do (Then Actions) else do (Else Actions)
If - Conditions
(("some player") Current lumber) Equal to X
Then - Actions
Actions... Remember to reduce lumber for that player.
Else - Actions
Unit - Order (Casting unit) to Stop
Game - Display to (All players) for Y seconds the text: text

I think this would work.