vb Code:
Dim d As Document, somefolder As String, myfile As String, myfooter As String
Dim myheader As String
somefolder = Environ("userprofile") & "\My Documents\"
myfile = Dir(somefolder & "*.doc")
Do While Len(myfile) > 0
Set d = Documents.Open(somefolder & myfile)
myheader = d.Sections(1).Headers(1).Range.Text
Select Case Left(myheader, Len(myheader) - 1)
myfooter = "some address"
myfooter = "someother address"
Case Else
myfooter = "generic address for other cases"
End Select
d.Sections(1).Footers(1).Range.Text = myfooter
myfile = Dir
Loop
this look for the files in somefolder, (my documents, in the code), you can expand the select case for all your addresses, if the headers or footers contain additional text you will have to modify the routine to find or add the bits you want