UITableViewCellAccessoryCheckmark multiple selection/detect which cells selected?

UITableViewCellAccessoryCheckmark multiple selection/detect which cells
selected?

I have a UITableView that shows UITableView cells with the
UITableViewCellAccessoryCheckmark option enabled. I would like to let the
user select multiple cells to their liking and when their done, press a
"Done" button.
However, when the "Done" button is pressed, I need to be able to add ONLY
the selected object from the UITableView array into a separate array.
cell.accessoryType = UITableViewCellAccessoryCheckmark;
To recap: User can select as many cells as they want. When done, they
press a UIButton which then adds ONLY the selected cells to another array.
Thank you for your help in advance!