Int 21 Fn 3501  P - Flashtek X-32vm - Allocate Protected-mode Selector     [E]

   AX = 3501h

Return: CF clear if successful
       BX = new selector
   CF set on error (no more selectors available)

Note:  the new selector will be an expand-up read/write data selector with
     undefined base and limit

See Also: AX=3502h,INT 31/AX=0000h