You'd do it this way:

Code:
global script Slot_2{
   void run(){
       while(true){
      //call the ladder function
         ladder(98);
          Waitframe();
        }
     }
 }
global variablies and constants goes on top of the global script file, each variable ending in a semi-colon.

you can also change the variable 98 to any other flag number of your choice. you can only use flags 98 - 102 for now though.