Hi,

If Comment column is column 5 then this SelectionChange code results in
a temporary text box containing the active cell's contents and is
positioned over the top of the selected cell.


Public ShpMsg As Shape
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
If ActiveCell.Column = 5 Then
On Error Resume Next
ShpMsg.Delete
If ActiveCell.Value < "" Then
Set ShpMsg = Me.Shapes.AddTextbox(msoTextOrientationHorizontal, _
ActiveCell.Left, ActiveCell.Top, 0, 0)
ShpMsg.TextFrame.Characters.Text = ActiveCell.Value
ShpMsg.TextFrame.AutoSize = True
End If
End If
End Sub

Copy code, right click sheet tab, select "View Code" from popup menu,
paste into Sheet's code module, press Alt + F11 to get back to Excel.
Security must be medium and "Enable Macros" button clicked on "Security
Warning" dialog when opened.

3 years to go before I retire so I'm probably too young!

Ken Johnson