Rejecting Execution 
You can use this function if you need to reject execution of a work item for business or technical reasons. This function is only available for Dialog Work Items.
Example
The table entry to be processed already exists or the material whose master data is to be changed is no longer used.
This function is only available if the property processing rejectable has been selected for the related step in the workflow definition .
Processing of the work item is terminated with the reject execution function. The subsequent steps defined in the workflow definition are executed.
Do not use this function if you do not want to or cannot process the work item for personal reasons (not responsible, not competent). In this case, replace a reserved work item or forward it.
You can access this function in the Business Workplace by choosing
(Other Functions) or the work item display ().