codice:
Public Function IsFormLoaded(ByVal FormName As String) As Boolean
    Dim frm As Form
    IsFormLoaded = False
    For Each frm In Forms
        If UCase(frm.Name) = UCase(FormName) Then
            IsFormLoaded = True
        End If
    Next frm    
    Set frm = Nothing   
End Function
lanci questa funzione sull'evento che carica il form se ritorna false lo carichi altrimenti no