Apple Numbers '09 - Manual (Page 126)

To specify a value to replace any argument placeholder, click the argument placeholder
and type a constant or insert a cell reference (see “Referring to Cells in Formulas” on
page 126 for instructions). If the argument placeholder is light gray, providing a value
is optional.
Handling Errors and Warnings in Formulas
When a formula in a table cell is incomplete, contains invalid cell references, or is
otherwise incorrect, or when an import operation creates an error condition in a
cell, Numbers displays an icon in the cell. A blue triangle in the upper left of a cell
indicates one or more warnings. A red triangle in the middle of a cell means that a
formula error occurred.
To view error and warning messages:
Click the icon.
m
A message window summarizes each error and warning condition associated with
the cell.
To have Numbers issue a warning when a cell referenced in a formula is empty, choose
Numbers > Preferences and in the General pane select “Show warnings when formulas
reference empty cells.”
Removing Formulas
If you no longer want to use a formula that’s associated with a cell, you can quickly
remove the formula.
To remove a formula from a cell:
1 Select the cell.
2 Press the Delete key.
If you need to review formulas in a spreadsheet before deciding what to delete,
choose View > Show Formula List.
Referring to Cells in Formulas
You use cell references to identify cells whose values you want to use in formulas. The
cells can be in the same table as the formula cell, or they can be in another table on
the same or a different sheet.
126 Chapter 6 Using Formulas in Tables