Fire 'Worksheet_Change' event only when cell value is actually different - vba

Question

I wrote code to extract data from the URL a particular page.
First time I run the code it extracts data from URL to cell C1.
I am at a point where I want to display a MsgBox whenever cell value changes.
For example:
First time I run the code "Happy" gets extracted to cell C1.
(Cell value changes, so msgbox "value changed")
The second time I run the code then Also "Happy" gets extracted to the cell C1.
(means no change, Noting happens)
The third time I run the code and "Sad" gets extracted to cell C1,
so at this point, I want a msgbox of the cell change.
I tried the below code but it shows the msgbox even when same values are changed in the cell.
For example - Cell contains text "Happy". I rewrite "Happy" in cell and press enter, so it displays msgbox of cell changed despite being same text in the cell.
Private Sub Worksheet_Change(ByVal Target As Range)
Dim KeyCells As Range
' The variable KeyCells contains the cells that will
' cause an alert when they are changed.
Set KeyCells = Range("A1:C10")
If Not Application.Intersect(KeyCells, Range(Target.Address)) Is Nothing Then
' Display a message when one of the designated cells has been
' changed.
' Place your code here.
MsgBox "Cell " & Target.Address & " has changed."
End If
End Sub

Answer 1

This uses Undo to check what the previous value of the cell was, and then compare it to the new value.
This will also not be case-sensitive, so HAPPY = HAPpy. If you want it to be case sensitive then remove the strconv functions.
Note that (any) of these procedures (including yours) will not react properly to multiple cells changing at once (like pasting in a range of cells), but you could add code to handle that however you needed to as demonstrated in the commented out lines.
But for single cells, this will do the trick:
Private Sub Worksheet_Change(ByVal Target As Range)
Dim KeyCells As Range, vNew, vOld
If Target.Cells.Count > 1 Then
MsgBox ("multiple cells changed: " & vbLf & Target.Address)
'to handle multiple cells changing at omce you'll need to loop like:
' dim c as cell
' for each c in Target.Cells
' ... etc
Exit Sub
End If
Set KeyCells = Range("A1:C10") ' cells to watch
If Not Application.Intersect(KeyCells, Target) Is Nothing Then
vNew = Target.Value
Application.EnableEvents = False
Application.Undo
vOld = Target.Value
Target.Value = vNew
Application.EnableEvents = True
'make sure value is different (NOT case sensitive)
If StrConv(vNew, vbLowerCase) <> StrConv(vOld, vbLowerCase) Then
'do something here
MsgBox "Cell " & Target.Address & " changed" & vblf & _
"From: " & vOld & vblf & _
"To: " & vNew
End If
End If
End Sub
More Information:
MSDN : Application.Undo Method (Excel)
MSDN : Application.EnableEvents Property (Excel)
MSDN : Worksheet.Change Event (Excel)
Stack Overflow : How do I get the old value of a changed cell in Excel VBA? (Ronnie Dickson's answer)

Answer 2

Replace:
If Not Application.Intersect(KeyCells, Range(Target.Address))
with:
If Not Application.Intersect(KeyCells, Target)

Answer 3

Try it like this:
Public PrevValue
Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
If Target.Value <> PrevValue Then
MsgBox ("value changed")
PrevValue = Target.Value
End If
End Sub
The previous value is now stored in the global variable. When the value changes, it first checks if the value is the same as the previous value.
Edit:
If you change different cells each time, you can also use
Private Sub Workbook_SheetSelectionChange(ByVal Sh As Object, ByVal Target As Range)
PrevValue = Target.Value
End Sub
To set the value of the currenctly selected cell before the change.