Almost all of the built-in worksheet functions can be used in macros.
If you have a non-English version of Excel you have to remember to use the English function names,
and that the separator sign between the function arguments always is a comma (,).
If you don't know the English function name, record a macro while you enter the function the usual way in a cell,
in the registered macro the function name will be translated to English.
When you are going to use a worksheetfunction in a macro you also have to include the Application-object.
In Excel97 you use the object Application.WorksheetFunction.
Examples:
MyTotal = Application.Sum(Range("A1:A100"))
' returns the total of the values in A1:A100 in the active worksheet.
MyTotal = Application.WorksheetFunction.Sum(Range("A1:A100"))
' the same formula for Excel 97.