Formula that uses Previous Sheet name

I have created an excel workbook (2007) with multiple pages for payroll hours submission. Each sheet accrues flex time and I need this accrual to carry forward to the next pay period. I would like a formula that will use the name of the previous tab in the current sheet. Current formula is:

='May 15 - May 30'!J25

Unfortunately, I have to manually update each formula with the sheet name. Is it possible to build a formula that will do this for me?

~Amy