Combobox items based on choice in previous combobox

I think I'm on to something here. I'm just not getting the code right.

Num Comment
1 this is the comment for the first example of number 1.
1 This is the second comment for number one.
2 This is the only comment for nymber 2.
3 Comment for number 3
5 First comment for number 5
5 Second comment for number 5.
5 Third comment for number 5.
6 Only comment for number 6.
7 One of two comments for number 7.
7 The other comment for number 7.

I have a table or range that looks like above. Notice repeated numbers
in first column.
I use a little procedure to get only the unique values in Num column
to populate a combobox.
The next thing would be to select one of those numbers, 5 for example,
and populate a combobox
with only the three comments associated with that number. It occurred
to me that defining and then adding items selectively, based on
criterion might be the way. Below is my attempt but it doesn't quite
work.

Private Sub ComboBox5_Change()

Dim rng As Range, i As Long
Dim SelectedComments As New Collection, Item

For i = 1 To
Worksheets("Sheet2").Range("ReferenceGuide").Rows.Count
Set rng = Worksheets("Sheet2").Cells(i, 2)
If rng.Offset(0, -1).Value = ComboBox5.Value Then
SelectedComments.Add rng.Value, CStr(rng.Value)
End If
Next

For Each Item In SelectedComments
UserForm1.ComboBox6.AddItem Item
Next Item
End Sub