Specify Size of Comment

I have a macro which tracks changes to cells within a worksheet by adding comments to changed cells. . . .

Private Sub Worksheet_Change(ByVal Target As Excel.Range)
On Error Resume Next
here = Target.Address
newnum = Target.Value
oldnum = Sheets("historical data").Range(here).Value
If oldnum = "" Then GoTo line99
oldcomment = Target.Comment.Text
Target.AddComment
Target.Comment.Text oldcomment & "Modified: " & Date & " " & Time & " by " & Application.UserName & ". Previous value was " & oldnum & Chr(10)
line99:
Sheets("historical data").Range(here).Value = newnum
End Sub

This works nicely, but the only slight problem is that the default comment size is too small.

Is there any way to either change the default size of a comment or to specify the required size when the comment is created?

JAF