Thank you suggesting Python idea.
but I already coded my function in C#, and I don't have time to convert it (as I said, I have limited experience in programing).
Also, from my experience, python is slower than C#, and for my function, computing time is important.
So, I need way to make simple GUI with C#.
In ESRI walkthrough, they just mentioned about tools and buttons. How can I create simple tool window with GUI, just like ArcTool??