Hi Wolfgang,
Sorry for the delay.
I dont think there is any such requirement while adding a hyperlink.
AutoCAD tries to resolve the actual path only when you click on the entity with Ctrl pressed.
Using this code, I could add a hyperlink to a file that did not exist and AutoCAD displayed the error message only when the entity was clicked.
HyperLink hyperLink = new HyperLink();
hyperLink.Description = "My File";
hyperLink.Name = "..\\..\\..\\..\\..\\..\\..\\..\\Temp\\5.txt";
hyperLink.SubLocation = "";
linkCollection.Add(hyperLink);
Balaji
Developer Technical Services
Autodesk Developer Network