BG --
Do you mean "worksheet" or "workbook"? Actually, either way it's the same
basic approach. To pull information from one sheet to another inside the
same workbook, select the target cell (to be updated), press '=', then select
the source cell, and press enter. You can also make that reference part of a
larger equation.
Pulling info from another workbook is same process. Have them both open.
In the target cell, press '=', then select the source cell in the other
workbook. When you open the target workbook, it will automatically open the
other workbook to get information from it. Again, you can use that refernce
as part of a larger equation.
HTH