Private guid As Guid = New Guid("01bc2dbd-561b-4779-3a92-dda4f12bdb6d")
...
Public Sub UnMake_It(commandData As ExternalCommandData)
Dim uiDoc As UIDocument = commandData.Application.ActiveUIDocument
Dim Doc As Document = uiDoc.Document
Dim tr As New Transaction(Doc, "Extensible Storage")
' Находим все семейства выборкой
Dim coll As FilteredElementCollector = New FilteredElementCollector(Doc).OfClass(GetType(Autodesk.Revit.DB.Family))
Dim acElFam As Autodesk.Revit.DB.Element = Nothing
' Перебираем все семейства в выборке на предмет поиска созданных семейств
For Each acEl As Autodesk.Revit.DB.Element In coll
Dim acEl_IsOwnFamily As Family = CType(acEl, Family)
Select Case acEl_IsOwnFamily.IsOwnerFamily
Case True
acElFam = acEl
tr.Start()
Dim mySchema As Schema = Schema.Lookup(guid)
acElFam.DeleteEntity(mySchema)
tr.Commit()
tr.Dispose()
End Select
' Если созданных семейств не найдено, то выходим из процедуры
If acElFam Is Nothing Then
MsgBox("Удалять нечего!")
Exit Sub
End If
Next
End Sub