Connect Springs to Immovable Vertices

[fabianpal]

Hi,
I want to attach a spring between a part of the simulated object and another vertex that only moves when I update its position. I assume that one would use target points for that, but I do not want these points to interact with the fluid in any way. Is there a way to use vertices that do not interact with the fluid or a method to simply apply a force to a vertex of my shape in an arbitrary direction without using additional vertices?
Best regards,
Fabian