Replace checkbox in MailEnvelop with custom value - vba

Question

I need to send an document as email body. The document contains several { FORMCHECKBOX } fields, which are either selected or not. Now, whenever I actually send the email, the checkboxes are not included at all. Because of this issue, I thougth about replacing the checkboxes with "Yes" or "No", depending on the selection.
I found this code, to replace all checkboxes, but it doesn't care for the actual selection:
Sub ChkBxClr()
Dim i As Long, Rng As Range
With ActiveDocument
For i = .FormFields.Count To 1 Step -1
With .FormFields(i)
If .Type = wdFieldFormCheckBox Then
Set Rng = .Range
.Delete
Rng.Text = "[__]"
End If
End With
Next
Set Rng = Nothing
End With
End Sub
Also this code changes the whole document and not just the email body, which I would like to prevent.
The overall code:
Sub SendEmail()
Dim Subject As String
Dim From As String
On Error Resume Next
Selection.GoTo What:=wdGoToBookmark, Name:="From"
From = Selection.Text
Subject = "Title"
Call ChkBxClr
ActiveWindow.EnvelopeVisible = True
With ActiveDocument.MailEnvelope.Item
.To = "<some mail address>"
.Subject = Subject
.Send
End With
End Sub
Sub ChkBxClr()
Dim i As Long, Rng As Range
With ActiveDocument
For i = .FormFields.Count To 1 Step -1
With .FormFields(i)
If .Type = wdFieldFormCheckBox Then
Set Rng = .Range
.Delete
Rng.Text = "[__]"
End If
End With
Next
Set Rng = Nothing
End With
End Sub
So the question is, how can I either display the checkboxes within the email body or replace the checkboxes (preferably only in message body) with a text, depending on the selection?