Great, Paul, this does it indeed!
I now used Nz:
WHERE (((melding.status) Like Nz([Forms]![Versie keuze]![Versiebeheer subform].[Form]![Status],"*")))
I still do not understand why "*" did not work and "Bij VWA" did work correctly (both without the like-operator). But well, with Nz-solution it...