NT ontape batch job

Hello - I want to schedule nightly backups of our online server which runs on an NT platform. I have created a batch file - piping in a carriage return to deal with the 'mount tape' prompt - and then piping out the results to a file. My difficulity is with the 'at' scheduling - when the batch file runs from at - the result is a message that you must be dba to run the ontape utility. I have place all of the usual environment variables within the batch job - but can not seem to hit the one that would give the job permission to run the utility. Has any one encounter this or come up with a solution for running an ontape backup from 'at'. thanx - James Cardwell