For that you'd need to employ a ContentControlOnExit in the ThisDocument module of the document or its template, coded along the lines of:
Code:
Private Sub Document_ContentControlOnExit(ByVal CCtrl As ContentControl, Cancel As Boolean)
Select Case CCtrl.Title
Case "MyCheck"
With ActiveDocument.SelectContentControlsByTitle("MyCheck")
If CCtrl.Tag = "Yes" Then
.Item(2).Checked = Not CCtrl.Checked
ElseIf CCtrl.Tag = "No" Then
.Item(1).Checked = Not CCtrl.Checked
End If
End With
End Select
End Sub
Where the pair of checkbox content controls both have the Title 'MyCheck' and one of the pair has the Tag 'Yes' whilst the other has the Tag 'No'.
See attached.