Doug,
Address(rownumber,columnnumber) returns a string with the address of the cell equivalent of ActiveSheet.Cells(rownumber,ColumnNumber). The thir argument in the address function forces the Address function to return a string representing a relative reference.
For example,
=Address(1,2,4) would return "B1"
Because the rownumber fed to the address function in this case is always 1, the substitute function is used to replace 1 with "", leaving the column Letter(s).
[Edit]
=Column() returns the column number of the hose cell, so
=Address(1,2,4) would return a string containing the relative reference of the first cell in the column of the host cell.