Using GTP NET to design Gantt charts.Unfortunately, from what it seems, you can't add more than one time item link to predecessor in a Gantt chart using GTP.NET. I recommend you contact the developers and ask for help. You can get in touch with them using Support and contact page.
GTP.NET is a component package for .NET. The components helps you with time visualization and interaction. GTP.NET contains a fully interactive Gantt chart and a fully interactive Schedule chart.
GTP.NET components can be delivered via WindowsForms applications, ASP.NET, Microsoft Ajax and even in reduced trust environments like ClickOnce and XBAP. GTP.NET is runtime license free.
TP.NET 3.0 contains a sample series named "LetsBuild_". Currently there are 3 distinctively different samples in this series. They are "LetsBuild_ProjectPlanner", "LetsBuild_ResourceBooker" and "LetsBuild_WeeklyPlanner".