You could use a PopupGalleryTool. Set MaxDropDownColumns to 1. Then add a gallery tool item for each undo item to the Items collection of the gallery. This will give you the items in the list with the scrollbar. Then add a LabelTool to the Tools collection of the gallery to display how many items will be undone. You can handle the toolbars manager's GalleryToolActiveItemChange event to know when the user mouses over another item. The only issue you will have is that only one item in a gallery can be active or appear selected, so you will need to iterate over all Items in the gallery before the active item and change their appearance to appear selected as well. Also, if this gallery will appear in a ribbon group, set ShowPreviewInRibbon to False on the gallery.