I have 12 different worksheets for each month in a year in one workbook. In
each month's worksheet, I want year-to-date figures up to that month. All
the worksheets have the same fields in same cells. I prepare one worksheet
with all data and formulas for one month. Then I name the worksheet "Jan"
for January and copy that worksheet 11 times and rename them according to
individual months.

How can I insert a common formula that will work in every worksheet for
getting the year-to-date figures in each month's worksheet?

Thanks in advance for your time.