Mutually exclusive check boxes

Hello,

I'm trying to create mutually exclusive check boxes and after some searching, have found a macro that allows me to do so. I've attached a spreadsheet that has the functioning macro in it, however there is 1 small problem. When I select 'Yes' in the attached sheet, it deselects the 'CheckBox1' option. Once I've selected either Yes, No or Unsure, I can go back and select 'CheckBox1' again and this time it will save both options.

What I want to be able to do is select either 'CheckBox1' or/and 'Checkbox2' (so these 2 options are not mutually exclusive). Then I want to also be able to select either 'Yes', 'No' or 'Unsure' without it unselecting the previous selections (i.e. these 3 options are mutually exclusive of eachother, and are exclusive of the first 2 options).

Can anyone help with what I'm sure is a real simple fix to the code I'm using?

Thanks very much
Gareth

*Edit - server won't let me attach the excel file, so I've attached a screen dump of my example, and code is below:

Private Sub Yes_Change()

    With Me.Yes
        If .Value Then ClearGroup .GroupName, .Name
    End With

End Sub

Private Sub No_Change()

    With Me.No
        If .Value Then ClearGroup .GroupName, .Name
    End With

End Sub

Private Sub Unsure_Change()

    With Me.Unsure
        If .Value Then ClearGroup .GroupName, .Name
    End With

End Sub

Private Sub ClearGroup(sGroup As String, sName As String)

    Dim ole As OLEObject

    For Each ole In Me.OLEObjects
        If TypeName(ole.Object) = "CheckBox" Then
            If ole.Object.GroupName = sGroup And ole.Name <> sName Then
                ole.Object.Value = False
            End If
        End If
    Next ole

End Sub