Find and replace

You're very welcome! :)

This is an interesting question and it's actually pretty easy, but it requires a macro.

Here is a small macro that I made that had 2 pop-up windows, one for the value to search for and 1 for the value to use as a replacement. Once it runs, it will show a window with a count of how many values were replaced.

Sub ReplaceComments()

Dim eComment As Comment
Dim eSheet As Worksheet
Dim valueFind As String
Dim valueReplace As String
Dim commentText As String
Dim numberReplaced As Long

numberReplaced = 0

valueFind = InputBox("Value to find:")

valueReplace = InputBox("New value to replace old value with:")

For Each eSheet In Sheets

    For Each eComment In eSheet.Comments

        commentText = eComment.Text

        If InStr(commentText, valueFind) <> 0 Then

            commentText = Application.WorksheetFunction. _
            Substitute(commentText, valueFind, valueReplace)
            eComment.Text Text:=commentText

            numberReplaced = numberReplaced + 1

        End If

    Next

Next

If numberReplaced > 0 Then
    MsgBox numberReplaced & " replacements made."
Else
    MsgBox "Nothing found to replace."
End If

End Sub

I just made this but only tested it a little bit.

Let me know how it works :)