How returning to the same directory ago?

Question

I have create next path:

StringBuilder sb = new StringBuilder();
            sb.Append(Environment.CurrentDirectory.ToString());

Its path: d:\????????????????\?#\My projects\MyToolBar(new)\TestToolBar\TestToolBar\bin\Debug\

And i need: d:\????????????????\?#\My projects\MyToolBar(new)\TestToolBar\TestToolBar\bin\
How returning to the same directory ago?