Timer Job

Hi,

I want to run a custom SharePoint Job manually. Whenevert I wanna try to call RunNow() method it's showing access denied.

var traceJob = (from SPJobDefinition job in MainWebApp.JobDefinitions
                                              where job.DisplayName.ToLower().Replace(" ", "").Equals(jobDisplayName)
                                              select job).SingleOrDefault();
                              if (traceJob != null)
                              {
                                 traceJob.RunNow();
                              }

Shubho