Question

How to return comment as a cell from a conditional.

Example:

=if(a1=0;insert comment on cell)

insert comment and show comment

Answer 1

I could not find any way with default worksheet functions, so you might have to declare your own function for this – like this:

Public Function GetComment(rng As Range) as String
  GetComment = rng.NoteText
 'also possible
 'GetComment = rng.Comment.Text
End Function

Save this function into a Module, so it is accessible as a worksheetfunction.

then use =if(a1=0;GetComment(A1)) to return the comment.

edit:

Because I might have misunderstood a bit – here is a verison, which adds a comment to the caller-cell, sets its content to the given comment and makes the comment visible.

Public Function AddCmt(strComment As String) As String
  Dim rngCaller As Range
  If TypeName(Application.Caller) Like "Range" Then
    Set rngCaller = Application.Caller
    With rngCaller
      If .Comment Is Nothing Then
        .AddComment (strComment)
      Else
        .Comment.Text strComment
      End If
      .Comment.Visible = True
    End With
    'set caller-cell content to given comment
    AddCmt= strComment
  End If
End Function