[quote user="quasi_modo"]We are using Speedikon Architecture together with MicroStation (for some users we use PowerDraft instead of MicroStation - but I think that this should not make a difference here).[/quote]
Unfortunately it will make a difference. Jan's analysis is correct: you can't do what you want with VBA but it's easy to implement with MDL. However, a native-code MDL application won't run on a Power platform without a special key. The key must be obtained from Bentley Systems to enable the MDL app. to work with PowerDraft.
[quote user="quasi_modo"]Exit the drawing without saving the changes and open it again you will see that the Microstation things are still here while the Speedikon Objects are missing[/quote]
Speedikon must be doing something unusual for their graphic elements not to be made a permanent part of the DGN file. A long-term solution would be to persuade Speedikon to follow MicroStation's idiom of saving all graphic elements automatically.