How can I write a formula to reference a specific cell in a worksheet
immediately preceeding (or immediately after) the worksheet I'm in?

For instance:
If I'm in a worksheet called Week 11 I want my formula to reference a cell
in a worksheet called Week 10. Now I write the formula like this: =H29+'Week
10'!H31. However, I have a bunch of these formulas and a bunch of these
worksheets. Every week I'm in a new sheet, but I always have to look at cell
H31 from the prior week. For now when I generate a new worksheet I copy an
existing one then manually change each formula with the new sheet reference.
Tedious. I'd like to get away from that.

Is there a way for the formula to look something like this: =H29+'Previous
Worksheet'!H31 ?? That way I won't have to manually change it.