Add Checkboxes that will return emails addresses in the BCC field into Outlook

I am building an email in Excel for Outlook using the following code:

    Sub Mail_Selection_Range_Outlook_Body()
    'Don't forget to copy the function RangetoHTML in the module.
    'Working in Excel 2000-2016
        Dim rng As Range
        Dim OutApp As Object
        Dim OutMail As Object
    
        Set rng = Nothing
        On Error Resume Next
        'Only the visible cells in the selection
        'Set rng = Selection.SpecialCells(xlCellTypeVisible)
        'You can also use a fixed range if you want
        Set rng = Sheets("Volume Template").Range("K4:L14").SpecialCells(xlCellTypeVisible)
        On Error GoTo 0
    
        If rng Is Nothing Then
            MsgBox "The selection is not a range or the sheet is protected" & _
                   vbNewLine & "please correct and try again.", vbOKOnly
            Exit Sub
        End If
    
        With Application
            .EnableEvents = False
            .ScreenUpdating = False
        End With
    
        Set OutApp = CreateObject("Outlook.Application")
        Set OutMail = OutApp.CreateItem(0)
    
        On Error Resume Next
        With OutMail
            .To = ""
            .CC = ""
            .BCC =
            .Subject = "UTS VOLUME QUOTE REQUEST"
            .HTMLBody = RangetoHTML(rng)
            .Display   'or use .Send
        End With
        On Error GoTo 0
    
        With Application
            .EnableEvents = True
            .ScreenUpdating = True
        End With
    
        Set OutMail = Nothing
        Set OutApp = Nothing
    End Sub
    
    
    Function RangetoHTML(rng As Range)
        Dim fso As Object
        Dim ts As Object
        Dim TempFile As String
        Dim TempWB As Workbook
    
        TempFile = Environ$("temp") & "\" & Format(Now, "dd-mm-yy h-mm-ss") & ".htm"
    
        'Copy the range and create a new workbook to past the data in
        rng.Copy
        Set TempWB = Workbooks.Add(1)
        With TempWB.Sheets(1)
            .Cells(1).PasteSpecial Paste:=8
            .Cells(1).PasteSpecial xlPasteValues, , False, False
            .Cells(1).PasteSpecial xlPasteFormats, , False, False
            .Cells(1).Select
            Application.CutCopyMode = False
            On Error Resume Next
            .DrawingObjects.Visible = True
            .DrawingObjects.Delete
            On Error GoTo 0
        End With
    
        'Publish the sheet to a htm file
        With TempWB.PublishObjects.Add( _
             SourceType:=xlSourceRange, _
             Filename:=TempFile, _
             Sheet:=TempWB.Sheets(1).Name, _
             Source:=TempWB.Sheets(1).UsedRange.Address, _
             HtmlType:=xlHtmlStatic)
            .Publish (True)
        End With
    
        'Read all data from the htm file into RangetoHTML
        Set fso = CreateObject("Scripting.FileSystemObject")
        Set ts = fso.GetFile(TempFile).OpenAsTextStream(1, -2)
        RangetoHTML = ts.readall
        ts.Close
        RangetoHTML = Replace(RangetoHTML, "align=center x:publishsource=", _
                              "align=left x:publishsource=")
    
        'Close TempWB
        TempWB.Close savechanges:=False
    
        'Delete the htm file we used in this function
        Kill TempFile
    
        Set ts = Nothing
        Set fso = Nothing
        Set TempWB = Nothing
    End Function

I want to use check boxes (using the form controls) to decide whether an email is used.

If the check box reference cell is true input the value of a cell (an email address) into the BCC field.

If Cell H4=True return Cell F4.

Going down a list of about 30 entries so this needs to loop until there are no more check boxes

How do I write this code?