WAITNEXTXP expression [ , expression ]

   Synopsis:
      Pauses execution until the character's experience points (XP) required to
         reach the next level decrease

   Notes:
      The first expression is a number matching the experience points the
         character requires to reach the next level, which is usually different
         from their 'current' XP (depending on the world).
      The second expression is a timeout measured in seconds. If specified, the
         script gives up waiting after that period and resumes execution.
      WAITNEXTXP relies on the Status task to supply the character's required 
         XP. If the Status task is not running (or if it doesn't know anything 
         about the character's required XP), the Axbasic script pauses briefly 
         and resumes execution on the next task loop.
      See also the help for WAITEP, WAITGP, WAITHP, WAITMP, WAITSP and for 
         WAITXP and WAITTOTALXP.

   Requires:
      If the script is not being run as a task, the WAITNEXTXP statement is
         ignored (and no error message is generated). Execution continues with
         the next statement.
         
   Examples:
      ! Wait for required XP to fall below 1000
      WAITNEXTXP 1001
      ! Wait for no longer than five minutes (300 seconds)
      WAITNEXTXP 1001, 300
