If an employee manages to do this to you, I am afraid to say you are not an executive. Part of the skillset you need to have is to be able to get people to do the work you need them to. If this is happening there are few potential causes. 1. You failed to establish clear expectations from some one reporting to you and they have not realized it. 2. You are not perceived as a leader and there is no repercussions to disobedience. 3. You have a personality type that avoids conflict and implicitly shying away from taking it up with the employee. If it is case 2, I would either boot that employee out or change my job. Some times if you are in a leadership position without the clout it is almost impossible to get traction.