C# Language Extension

I am trying to create a C# language extension. That is, I want a language that looks like C# except it has certain additional lexical and syntactic features. For example I want to have this...

int i = 5 [m];

Where [m] indicates that the engineering units for the constant is meters.

Based on my understanding of the SynaxEditor .NET Languages Add-on I cannot do this without purchasing the source code for the Add-in and then modifying it.

Please confirm that my understanding is correct.

I would prefer to simply build my language extension by deriving a class from ActiproSoftware.SyntaxEditor.Addons.CSharp.CSharpSyntaxLanguage and then overriding a number of methods, but I am pretty sure (based on my reading of the manual and on various answers that have been given in the forum) that this path is a dead end.

Regards,

Bob Rundle