This  paper  is  concerned  with  the  problem  of  Just-In-Time  (JIT)  job  scheduling  in  a  dynamic  environment under  uncertainty  to  attain  timely  service.  We  provide an  approach,  based  on  robust  scheduling  concepts,  to analytically  evaluate  the  expected  cost  of  earliness  and tardiness for each job and also the project. In addition, we search for a schedule execution policy with the minimum robust cost such that for a given risk level , the actual realized schedule has  probability of completing with less than or equal to this robust cost. Our method is quite generic, and can be applied to JIT scheduling of jobs in a service company where earliness and tardiness are critical concerns.