I also support Italophile's advice, you should be storing the insertable formatted content into building blocks which can be retrieved anytime the macro requires it. Demo code to put it into a Rich Text Content Control looks like this.
Code:
Private Sub Document_ContentControlOnexit(ByVal aCC As ContentControl, Cancel As Boolean)
Dim aCC2 As ContentControl, sTag As String, aTemplate As Template
If aCC.Type = wdContentControlCheckBox Then
sTag = aCC.Tag
Set aTemplate = ActiveDocument.AttachedTemplate
Set aCC2 = ActiveDocument.SelectContentControlsByTitle(sTag)(1)
With aCC2
If aCC.Checked Then
aTemplate.BuildingBlockEntries("aa").Insert where:=aCC2.Range, RichText:=True
Else
aCC2.SetPlaceholderText Text:="Blank"
aCC2.Range.Text = ""
End If
End With
End If
End Sub