How do I retain data permanently in one worksheet from changing data from
another referenced worksheet in the same workbook. For example, every month
a particular workbook will be opened and saved as the current-period
worksheet. This work sheet has the past month data in it and will be
replaced with current period data. But I would like to retain the previous
data in another sheet in this workbook without re-typing the data in
manually. An example would be carrying monthly totals for the purpose of
calculating year-to-date totals.

Any suggestions would be appreciated!