Autocast help

[Norad III]

How to enable an autocast spell without right clicking on it? example: I upgrade scout tower to guard tower. scout tower doesn't have faerie fire but guard tower has it. ow to enable the autocast so that I don't need to right click on the spell of guard tower to activate it?

 

[13lack.1)ragon]

truly whos lazy enough NOT to click the ''right-click'' really