excel VBA run macro automatically whenever a cell is changed

In an attempt to find a way to make the target cell for the intersect method a name table array, I stumbled across a simple way to run something when ANY cell or set of cells on a particular sheet changes. This code is placed in the worksheet module as well:

Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Cells.Count > 0 Then
'mycode here
end if
end sub

In an attempt to spot a change somewhere in a particular column (here in "W", i.e. "23"), I modified Peter Alberts' answer to:

Private Sub Worksheet_Change(ByVal Target As Range)
    If Not Target.Column = 23 Then Exit Sub
    Application.EnableEvents = False             'to prevent endless loop
    On Error GoTo Finalize                       'to re-enable the events
    MsgBox "You changed a cell in column W, row " & Target.Row
    MsgBox "You changed it to: " & Target.Value
Finalize:
    Application.EnableEvents = True
End Sub

Yes, this is possible by using worksheet events:

In the Visual Basic Editor open the worksheet you're interested in (i.e. "BigBoard") by double clicking on the name of the worksheet in the tree at the top left. Place the following code in the module:

Private Sub Worksheet_Change(ByVal Target As Range)
    If Intersect(Target, Me.Range("D2")) Is Nothing Then Exit Sub
        Application.EnableEvents = False 'to prevent endless loop
        On Error Goto Finalize 'to re-enable the events      
        MsgBox "You changed THE CELL!"
    End If
Finalize:        
    Application.EnableEvents = True
End Sub

Another option is

Private Sub Worksheet_Change(ByVal Target As Range)
    IF Target.Address = "$D$2" Then
        MsgBox("Cell D2 Has Changed.")
    End If
End Sub

I believe this uses fewer resources than Intersect, which will be helpful if your worksheet changes a lot.