I would like to have an invoice number created by adding a number in the
previous sheet. Each year I create a spreadsheet that holds my time worked
for a client. I use this sheet as a invoice. I have each tab named based on
the bi-week I worked. I have a Macro that takes this name and places in in
my worksheet. At the bottom of my sheet I have a cell that references the
cell with the worksheet name. Above that I have an invoice number. On the
next sheet I reference that cell and add one. However, when I do that for
the next sheet I have to put in the sheet name. Is there a way to add from
previous sheet regardless of the name of the sheet?

On first sheet:
1. B39 has the starting invoice number for that year, i.e. 224
2. B40 has = D1
3. D1 has =WSN

Second sheet and each sheet I copy thereafter:
1. B39 has =='Dec 28, 2008 - Jan 10, 2009'!B39+1
2. B40 has = D1
3. D1 has =WSN

I want the formula in B39 to reference the previous sheet regardless of its
name instead of me always changing it to reflect the previous sheets name.