The XLL+ class library contains a number of classes to help with managing Excel's state. These can be used during macro add-in functions to help provide a more pleasant and predictable user experience.
Use CXlSuspendAutoRecalculation, CXlSuspendEcho and CXlSuspendError to improve performance and usability during macros.
Use CXlActiveBookRestorer, CXlActiveSheetRestorer and CXlActiveCellRestorer to restore the active book, sheet and selection after an operation is completed.