Limit entirerow columns with VBA code

Consider the following:

If a <> b then
Range("somerange").EntireRow.Font.Strikethrough = True
end if

It is a known fact that Excel 2007 has up to 16384 rows per sheet and that one does not want to format cells that are completely unused. Is there a way, using VBA code, to limit Excel to only use, say, 20 columns?