The answer is
no, not with C++ or C#.
To do this, you need to embed a runtime parser/compiler in your program and you need to have provision in the language to execute the result of compilation.
You will certainly find libraries that do this but certainly not in C++ because you will have problems to access local variables.
In fact, only semi-compiled languages (using some p-code) can do what you want. And the feature must be planned from the conceiving. You get this feature in VisualFoxPro and other languages from the same family.
In xBase family languages: FoxPro/dBase/xHarbour...
s="? 'Hello World!22'";
?"Hello World!11"
$ s
? "Hello World!33"
the $ calls the internal compiler on fly at runtime.
xHarbour comes with an utility "xPrompt" (open source) that is an interactive console app which embed a full featured parser/compiler. it can load and run a full program that is in a file as source code.