Cell by cell diff in excel - vba

Question

I've seen a couple similar questions, but nothing I've found quite hits the mark with me.
I have two tables on two different sheets. The tables themselves are structured identically, but hold different content. Each data cell within the table can have MULTIPLE lines of information (e.g. E5 is 5 lines (actual lines, not wrapped) of data).
I'd like to create a third table that is also structurally identical (row 1 and column A are the same) to the first two, but have each data cell contain in some meaningful syntax the difference between the same two cells in the first two tables. It could be as straightforward as the output of a diff between the contents of the first two cells.
Is there a way to essentially take the diff of sheet1!E5 and sheet2!E5 and store it in sheet3!E5 ?
EDIT:
Some clarification. All the data cells contain information on MULTIPLE lines. Some lines are present in one sheet but not in another. For instance, sheet1!E5 may contain "string1", "string2", and "string3" on THREE lines whereas sheet2!E5 contains "string2", "string3", "string7", and "string8" on FOUR lines. The output on sheet3!E5 could be anything that clearly marks the difference between the two, for instance (as was mentioned before), exactly what the output would be if the two cells were text files and you ran a diff (or diff -c) on them like this:
*** 1,3 ****
- string1
string2
! string3
\ No newline at end of file
--- 1,4 ----
string2
! string3
! string7
! string8
\ No newline at end of file
or even just something much simpler that lists the strings that are/are not in each cell like:
< string1
<> string2
<> string3
> string7
> string8

Answer 1

Using the code at https://en.wikipedia.org/wiki/Longest_common_subsequence_problem I made the following VBA code. It isn't verbatim because VBA doesn't allow short circuit operators and I needed PrintDiff to return the string instead of displaying it.
Function LCSLength(C() As Integer, X() As String, Y() As String, M As Integer, N As Integer) As Integer
Dim I As Integer
For I = 0 To M
C(I, LBound(Y)) = 0
Next
Dim J As Integer
For J = 0 To N
C(LBound(X), J) = 0
Next
For I = 1 To M
For J = 1 To N
If X(I) = Y(J) Then
C(I, J) = C(I - 1, J - 1) + 1
ElseIf C(I, J - 1) < C(I - 1, J) Then
C(I, J) = C(I - 1, J)
Else
C(I, J) = C(I, J - 1)
End If
Next
Next
LCSLength = C(M, N)
End Function
Function PrintDiff(C() As Integer, X() As String, Y() As String, I As Integer, J As Integer) As String
Continue = 1
If Continue = 1 And I > 0 And J > 0 Then
If X(I) = Y(J) Then
PrintDiff = PrintDiff(C, X, Y, I - 1, J - 1) & Chr(10) & "<> " & X(I)
Continue = 0
End If
End If
If Continue = 1 And J > 0 Then
If I = 0 Then
PrintDiff = PrintDiff(C, X, Y, I, J - 1) & Chr(10) & "> " & Y(J)
Continue = 0
ElseIf C(I, J - 1) >= C(I - 1, J) Then
PrintDiff = PrintDiff(C, X, Y, I, J - 1) & Chr(10) & "> " & Y(J)
Continue = 0
End If
End If
If Continue = 1 And I > 0 Then
If J = 0 Then
PrintDiff = PrintDiff(C, X, Y, I - 1, J) & Chr(10) & "< " & X(I)
Continue = 0
ElseIf C(I, J - 1) < C(I - 1, J) Then
PrintDiff = PrintDiff(C, X, Y, I - 1, J) & Chr(10) & "< " & X(I)
Continue = 0
End If
End If
If Continue = 1 Then
PrintDiff = ""
End If
End Function
Function Diff(A As String, B As String) As String
Dim X() As String
X = Split(Chr(10) & A, Chr(10))
Dim M As Integer
If (A = "") Then
M = 0
Else
M = UBound(X)
End If
Dim Y() As String
Y = Split(Chr(10) & B, Chr(10))
Dim N As Integer
If (B = "") Then
N = 0
Else
N = UBound(Y)
End If
Dim C() As Integer
ReDim C(M, N) As Integer
Call LCSLength(C, X, Y, M, N)
Diff = Mid(PrintDiff(C, X, Y, M, N), 2)
End Function
If A1 contains:
string1
string2
string3
And B1 contains:
string2
string3
string7
string8
And if C1 contains =Diff(A1,B1) then C1 will display:
< string1
<> string2
<> string3
> string7
> string8
According to the "Code optimization" section on that page several optimizations can be made to the code - I haven't done those in this code.

Answer 2

Yes. duplicate your structure in Sheet 3, and simply make sure all your references are accurate. For example, in cell A1 on sheet 3, you would just type:
= [navigate to sheet1!A1 and click it] - [navigate to sheet2!A1 and click it]
pretty easy, actually.