撤销按钮动作的下拉键，及下拉列表实现。通过点击撤销或返回列表中的某一列，可以直接撤销或返回到这一步。另可在按钮的提示框(ToolTips)上动态显示撤销或返回的具体信息。-revocation action of the drop-down button keys, and the drop-down list to achieve. By clicking on the entry list or revocation of a series can be directly withdrawn