Oracle DataFile move(online) in Windows

 Dear Experts, 

   Due to some space constraints, we have to move some database Files from one Drive to another in our database (11.2.0.2 on Windows 2008). 

   I tested the procedure of 

    SQL>> Alter tablespace <tbspce> offline;

    RMAN >> COPY DATAFILE X TO <<FILE_NAME>>;

    RMAN>> switch datafile x to copy;

 Then I tried to delete the dataFile in the old drive but I am not able to delete it, I am getting an error  "THE ACTION CAN'T BE COMPLETED BECAUSE THE FILE IS OPEN IN ORACLESDERVICE "

  Do I have any other options to do this activity in Windows when the DB is open as our customer is not open to downtime due to some business constraints.