AutoCAD .NET :: Deleting / Resetting Custom Properties?

I have been programming our document and version control values into the sheet set object, as a result the custom property list per drawing is getting a little large and is becoming a bit hard to manage. There are now properties with values that are no longer needed. Is there a way to delete or clear or maybe reset the customproperty bag per sheetset object / sheet object?

I have been playing around with code that looks like this:
 
Private Sub DeleteCustomProperties(ByRef myItem As IAcSmPersist, Optional ByVal Lock As Boolean = True) ''Throw New NotImplementedException Dim myDB As AcSmDatabase = myItem.GetDatabase Try Select Case myItem.GetTypeName Case "AcSmSheetSet" If True Then Dim mySheetset As AcSmSheetSet = myItem mySheetset.GetCustomPropertyBag.Clear() End If Exit Select Case "AcSmSheet" If True Then Dim mySheet As AcSmSheet = myItem mySheet.GetCustomPropertyBag.Clear() End If Exit Select End Select Catch ex As Exception End Try End Sub
 
but when i get to "set" the new custom properties (which works normaly when updating a custom property or adding a custom property to a custom propertybag that I have not "cleared"), I am getting a object not set to an instance error...

Do I have to "recreate" the custom propertybag with the InitNew(ByVal pOwner as IAcSmPersist).