To add a line break (line change) in a cell, use Cmd-Opt-Enter (Mac) or Alt-Enter (Windows).
In MS Excel Mac, it could be located in either /Users/<your user name>/Library/Application Support/Microsoft/Office/Excel or Users/<your user name>/Documents/Microsoft User Data/Excel
When Excel is opened and you want to see this "hidden" workbook, go to the Windows menu, then click Unhide...
=DATE(2012,12,31)
=WEEKDAY(DATE(2012,12,31))
Here are some Excel Visual Basic tips.
LastCellRow=ActiveSheet.UsedRange.Rows.Count
Ever got stuck because your Excel software is not in English and the tips you can find on the web have the English functions? Use this to translate Excel functions from one language to another: http://wwwhome.ewi.utwente.nl/~trieschn/excel/excel.html