After enabling the Auto Exposure Bracket feature, specifying the three exposure range you mentioned, use the "Interval timer shooting" option, selecting to shoot x3 photos at 1 second interval. Interval timer is located in the root level of the Shooting Menu.
Select Interval timer shooting menu option and press right arrow
Choose either "Now" as start time and press right arrow, or specify a delay time in hours/minutes before the first photo is taken
Using up/down and left/right arrows, set the interval between shots to 00:00:01 and press right arrow
At the next screen, use same up/down and left/right process and set the number of shots to "001 x 3 = 0003"
After you set the last number to "3" and press the right arrow once more, you will be presented with an "On/Off" prompt. Simply select on and press "OK" button to start the process
If you picked Now as the option for Step 2 above, the process will begin straight away. Otherwise, the camera will count down the amount of time specified before starting.
Note, after the interval timer is finished, the D7000 turns the interval timer function OFF. All of your previous settings like interval itself and number of shots remain, but you have to go back into the interval timer feature, use the right arrow through all the settings again until you get to the end where it asks the On/Off question.
This resetting to off is kind of a pain to me, and as a result, I have placed the entire Interval timer shooting menu as an item in the custom "My Menu" section for quicker access.