Controlling/Stopping Process Execution

Question

Has anyone here know how to stop an executable before it runs. I'm trying to make a software like Sanctuary(securewave.com). This product prevents execution of any program that does not appear on the list of software that is allowed to run on a particular machine. I have made some research about it and I found out that you have to go to kernel-mode and hook its API on NtCreateSection(). I know that I have to use ntdll.dll or kernel32.dll to accomplish this task. But I don't know how to use the imported dll in c#. I hope someone could me some snippet or guides.