Form & ActiveX Controls

You can use this and skip the Worksheet_Change event.

Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
    Dim rArea       As Range

    With Target
        If Intersect(.Cells, Range("Ckboxes")) Is Nothing Then Exit Sub
        Cancel = True
        Range("Ckboxes").Font.Name = "Marlett"

        For Each rArea In Range("Ckboxes").Areas
            If Not Intersect(.Cells, rArea) Is Nothing Then
                If .Value = "a" Then
                    .ClearContents
                Else
                    rArea.ClearContents
                    .Value = "a"
                End If
                
                Exit Sub
            End If
        Next rArea
    End With
End Sub

I've never added CODE tags...how do I do that?

Explained in the forum rules.