How can I add a button that updates all the functions I've placed?

If you set calculation to manual in Excel's settings Formulas tab, you can update the functions by pressing F9, or by creating a button that does the update. To create a button, follow these steps:

1. Open the VBA macro editor (to find the VBA editor in Excel 2007, check Options: Popular: Show Developer tab in the Ribbon. In Excel 2003, you can open the ditor from Tools: Macro: Visual Basic Editor).
2. In the editor, select Insert: Module .
3. In the module that opens, paste this code:
       Sub refreshAll()
           Application.Calculate
      End Sub
4. Close the Visual Basic editor and return to Excel.
5. In the Developer tab, choose Insert: Button (Form control).
6. When you have placed the button on the sheet, right-click and choose Assign macro, and as the macro name, type "refreshAll".