The initial post included this line
If Me.CheckBox1.Value
This made me think that you had the checkboxes on a VBA Userform since 'Me' is a reference to a VBA userform.
If you ACTUALLY have Content Control Checkboxes in the body of the document then the coding can be simpler. Put this code into the ThisDocument module. You won't need any other code if you have set up your Tag/Title combinations with the Content Controls.
Code:
Private Sub Document_ContentControlOnExit(ByVal aCC As ContentControl, Cancel As Boolean)
Dim aCC2 As ContentControl, sTag As String
If aCC.Type = wdContentControlCheckBox Then
sTag = aCC.Tag
Set aCC2 = ActiveDocument.SelectContentControlsByTitle(sTag)(1)
With aCC2
If aCC.Checked Then
aCC2.Range.Text = "Title" & vbTab & "First line"
aCC2.Range.Words(1).Bold = True
Else
aCC2.SetPlaceholderText Text:="Blank"
aCC2.Range.Text = ""
End If
End With
End If
End Sub