Let's say it's February and you need to link to the January totals.
Assume also that the tabs in your workbook are called Jan Feb Mar etc.
Click on the Feb tab, and land the cell pointer on the cell that hold
the January data. Start a formula by pressing the = sign, then click
on the Jan tab and click the cell with the carryforward total. Press
Enter, and the Feb tab will appear again, and reflect the January
number.

Since tab names change with month names, replicating the resultant
formulas could be accomplished with a macro. But since the entire
operation takes about 3 seconds the amount of time spent automating it
wouldn't generate a time savings.