Checkboxes, selecting

I dont see what I am doing wrong. If I select checkbox1 I want checkbox3 to be false and vice versa, thats simple enough. Everytime I click on one or the other checkboxes I have to reselect the one I want.

It takes two clicks to get a checkbox checked (True).
My listbox will be populated by both lists in the "Checkboxes" code once I select a checkbox, then reselct to repopulate.

Checkboxes:

    ListBox1.Clear
    CheckBox3.Value = False
    TextBox11.Font = "Tahoma"
    SaveSetting "GdtFcfBuilder", "Variables", "sStdFont", CheckBox1.Value
    SaveSetting "GdtFcfBuilder", "Variables", "sIMSFont", CheckBox3.Value

    ListBox1.Font = "Tahoma"
    With ListBox1
        .AddItem "- (Straigtness)"
        .AddItem "Flat (Flatness)"
        .AddItem "Rnd (Roundness)"
        .AddItem "ProL (Profile Line)"
        .AddItem "ProS (Profile Surface)"
        .AddItem "Ang (Angularity)"
        .AddItem "// (Parallelism)"
        .AddItem "Per (Perpindicularity)"
        .AddItem "TP (True Position)"
        .AddItem "Con (concentricity)"
        .AddItem "Sym (Symetry)"
        .AddItem "CiRo (Circular Runout)"
        .AddItem "ToRo (Total Runout)"
    End With
End Sub

Private Sub CheckBox3_Click()
    ListBox1.Clear
    CheckBox1.Value = False
    TextBox11.Font = "IMS"
    SaveSetting "GdtFcfBuilder", "Variables", "sStdFont", CheckBox1.Value
    SaveSetting "GdtFcfBuilder", "Variables", "sIMSFont", CheckBox3.Value

    ListBox1.Font = "IMS"
    With ListBox1
        .AddItem "³ (Straigtness)"
        .AddItem "ä (Flatness)"
        .AddItem "Î (Roundness)"
        .AddItem "ü (Profile Line)"
        .AddItem "æ (Profile Surface)"
        .AddItem "² (Angularity)"
        .AddItem "á (Parallelism)"
        .AddItem "ã (Perpindicularity)"
        .AddItem "û (True Position)"
        .AddItem "â (concentricity)"
        .AddItem "ÿ (Symetry)"
        .AddItem "ç (Circular Runout)"
        .AddItem "è (Total Runout)"
    End With
End Sub

Initialize userform:

Private Sub UserForm_Initialize()
'Set checkbox values on initialize
    CheckBox1.Value = GetSetting("GdtFcfBuilder", "Variables", "sStdFont")
    CheckBox3.Value = GetSetting("GdtFcfBuilder", "Variables", "sIMSFont")

    'Tahoma font
    If CheckBox1.Value = True Then
        TextBox11.Font = "Tahoma"
    End If
    'IMS Font
    If CheckBox3.Value = True Then
        TextBox11.Font = "IMS"
    End If

    CommandButton1.Caption = "Paste"
    CommandButton2.Caption = "Cancel"
    CommandButton3.Caption = "Information"

    With ListBox2
        .AddItem "Ø"
        .AddItem "Na"
    End With
End Sub

Any hints, tips or examples are appreciated.