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Write a formal letter for your request, CC it to the next person in command (his immediate supervisor).  Be sure to include the last times you made the requests and how.  Also, include the nature of your disability and the best way to reach you for an answer. If he does not respond in five business days, then take the letter and go to the next chain of command.  At that point, you can file a grievance with the Disability Support Office.  Keep going until you get an answer.