Note that these really aren't' constants, but are properties of the Rows
and Columns collection (which are child objects of Worksheet - not
qualifying them defaults to the ActiveSHeet).
Since the number of rows in a worksheet is version dependent, using this
method is superior to constants, since Rows.Count will return the number
of rows in the activesheet for XL4 (16757), and XL97-04 (65536) and will
return over 1,000,000 for XL12.