Back to my timesheet workbook...

I add a new sheet for each pay period (every two weeks). I name each
timesheet with the last date of the period (current sheet is 10.27.07;
previous one is 10.13.07).

To keep track of the amount of leave time accumulated I have to use cell
values from the previous periods timesheet. It is not a specific sheet; it
is relative, i.e. always the sheet preceeding the current one).

Currently, I manually change those cells to reflect the correct timesheet
name. Is there a way to refer to the relative timesheet in excel?