How To Get 3D Sum Against Increasing Number Of Sheet Tabs

My wife and I run an apartment complex with 2 employees, a manager and a maintenance man.

We use excel to produce a paystub for these employees twice a month.

There are a number of variables including incentives for renting apartments, overtime, variable hours in a pay period etc.

We have a separate spreadsheet for each employee and a separate sheet tab for each pay period named for the pay date... e.g. the first paystub had one sheet named "Jan 15"... the next pay period the paystub had 2 sheets: "Jan 31" and "Jan 15". The third paystub had 3 sheets and so on.

The paystubs have a column with the numbers for the pay period and then a column with the year to date sum (for straight pay, over time, federal withholding, social security, medicare, state withholding, etc.)

Right now I edit the formulas for all these sums for each payperiod. e.g. =sum('Feb 15':'Jan 15'!B35) for the third pay period is editted to =sum('Feb 28':'Jan 15'!B35) for the fourth pay period.

I would like to be able to just copy the prior spreadsheet and not have to find and replace values in 11 spreadsheet cells for each pay period.

I have figured out how to get the name of the current spreadsheet to appear in a cell on that sheet using VBA... but not how to get that cell content to be part of the arguments for =sum(. on the formula bar...