Office Timesheet Issue

Hello,

I recently started a job where there was a preexisting Excel timesheet set up in 2008 with pages (one for each month, all linked together so that Vacation time, sick time, over time, etc. would carry over from month to month.) The sheets ended with December 2012 and I don't know how to carry on the timesheets without messing everything up.

Help!

-Lindsey