detaching references with Display Off

Hi--

I found a .mvba that detaches all references that are turned off or missing.  What I need is to keep the missing ones that are turned on, or in otherwords, I only want to detach the references that are turned off.

Here is the .mvba that detaches all the off and missing references:
Sub detachDisplayOff()

For Each Attachment In
    ActiveModelReference.Attachments

    Set currentRef = Attachment

    If currentRef.ElementsVisible = False Then
        Dim attParent As ModelReference
        Set attParent =
            currentRef.ParentModelReference
        attParent.Attachments.Remove currentRef
    End If

Next

RedrawAllViews

End Sub

According to the webiste:
"Note: because of the way MicroStation's attachment objects are structured, this will detach
all references that have Display switched off and any reference that cannot be found
(ie show in the Reference dialogue box in red). If you want to get clever and ignore the
missing references you'll have to add a check on the value of .isMissingModel. " 
I'm just wondering if anyone can edit this .mvba to use this .isMissingModel, as I have
no idea what the code is.
Thanks.