There are some applications like Soundex that will do what you want at a
higher level. If you give Soundex Smith it will find smyth, smythe, etc.
However it does not work  at the letter by letter level and is rally a search
process rather than a comparison.

I do not know of anything which will do what you want - but there may be
something out there somewhere.

Another thing you would need to allow for is letters  out of order. Simth for
example.

Had no idea what Soundex was, but after
reading your message I found an article about it on wikipeda. Then I
found a Soundex example  on j-walk.com that looks like a good start.
You've been more helpful than you realize!

I agree that a Soundex routine is closer to what you
specified, but here is a function  that compares 2
strings and returns a percent (a double) indicating
how similar they are.

Public Function Str_Comp(st1 As String, st2 As String)
As Double
'From Analyzing Business Data with Excel, O'Reilly
Media
Dim MtchTbl(100, 100)
Dim MyMax As Double, ThisMax As Double
Dim i As Integer, j As Integer, ii As Integer, jj
As Integer
st1$ =
Trim(Application.WorksheetFunction.Proper(st1$))
st2$ =
Trim(Application.WorksheetFunction.Proper(st2$))
MyMax# = 0
For i% = Len(st1$) To 1 Step -1
For j% = Len(st2$) To 1 Step -1
If Mid(st1$, i%, 1) = Mid(st2$, j%, 1)
Then
ThisMax# = 0
For ii% = (i% + 1) To Len(st1$)
For jj% = (j% + 1) To Len(st2$)
If MtchTbl(ii%, jj%) >
ThisMax# Then
ThisMax# = MtchTbl(ii%,
jj%)
End If
Next jj%
Next ii%
MtchTbl(i%, j%) = ThisMax# + 1
If (ThisMax# + 1) > ThisMax# Then
MyMax# = ThisMax# + 1
End If
End If
Next j%
Next i%
Str_Comp# = MyMax# / ((Len(st1$) + Len(st2$)) / 2)
End Function

I have had good results with this function.