Int 21 Fn DF0B  - Software Carousel - Set Task Switch Callback             [T]

   AX = DF0Bh
   BH = interrupt number or 00h
   BL = function number to invoke on partition switch
   CL = function number to call when it is safe for resident programs
       to perform DOS calls
   DS:DX -> FAR function to call if BH=00h

Return: AL = status
       00h Carousel not running
       01h successful
       FFh unsucessful
       AH = error code (01h,03h) (see #1501)

Notes: the specified interrupt or FAR function is called with AH set to the
     appropriate one of the values specified in BL and CL, and BL set to
     the new task number
   the function specified by CL will not be called until the notification
     is enabled with AX=DF0Ch

See Also: AX=DF0Ch