Refresh Userform ComboBox Data Source

I have the following code in the Change procedure of a checkbox on a userfrom. What I want is if the box is checked then the ComboBox (SummaryFiles) gets its list from Col G of the Summary Files sheet, and if it is NOT checked then get it's list from column H. This IS NOT working for me at all. I have the Column H section in the Initialize code at first, but then if a user checks the Show All box then the list does not get refreshed, it gets appended to. Basically this list will show more files than what is on the sheet. It is not refreshing, it is appending this list.

Does anyone know how to make the source change from one column to another for a combobox?

Private Sub ShowAll_Change()

Dim Rng As Range
Dim i As Long
Sheets("Product Receipt").Select
    
    If ShowAll.Value = True Then
        Me.SummaryFiles.RowSource = ""
        Set Rng = Sheets("Summary Files").Range("G:G")
            For i = 1 To Rng.Rows.Count
                If Rng(i) <> "" Then
                    Me.SummaryFiles.AddItem Rng(i)
                End If
            Next i
    Else
        Me.SummaryFiles.RowSource = ""
        Set Rng = Sheets("Summary Files").Range("H:H")
            For i = 1 To Rng.Rows.Count
                If Rng(i) <> "" Then
                Me.SummaryFiles.AddItem Rng(i)
            End If
         Next i
         
    End If

Me.SummaryFiles.SetFocus

End Sub
Private Sub UserForm_Initialize()

Me.SummaryFiles.SetFocus

End Sub

After some trials and error, I came up with the following that does exactly what I was looking for. basically I swapped the code from the CheckBox Change and Initialize and also added a ComboBox.Clear line to the checkbox change code, the following works perfectly for me.

Private Sub ShowAll_Change()

Me.SummaryFiles.Clear
UserForm_Initialize

End Sub
Private Sub UserForm_Initialize()

Dim Rng As Range
Dim i As Long
Sheets("Product Receipt").Select
    
    If ShowAll.Value = True Then
        Me.SummaryFiles.RowSource = ""
        Set Rng = Sheets("Summary Files").Range("G:G")
            For i = 1 To Rng.Rows.Count
                If Rng(i) <> "" Then
                    Me.SummaryFiles.AddItem Rng(i)
                End If
            Next i
    Else
        Me.SummaryFiles.RowSource = ""
        Set Rng = Sheets("Summary Files").Range("H:H")
            For i = 1 To Rng.Rows.Count
                If Rng(i) <> "" Then
                Me.SummaryFiles.AddItem Rng(i)
            End If
         Next i
         
    End If

Me.SummaryFiles.SetFocus

End Sub