Dillip Kumar Mahapatra:
Thank you for your post.
At this time, you cannot stop a running schedule in FileMaker Server 11. Interrupting a schedule while it is in the middle of a process could have some damaging effects, so you may want to consider a way to stop a schedule after a certain break point. For example, create a Table that has one field to be set as a flag. After each script step, you can check to see if the flag is set. If 0, continue. If 1, stop. This allows you to start the schedule, and then you can set the flag to 1 if you made a mistake, and the schedule will stop after the currently run script step.
One caveat to this approach is that it doesn't let you know what script step was last executed, so you may also want to have an audit log to log the script steps that were executed before the script was stopped.
Let me know if you need additional clarification.