Addressing the three questions you asked in turn:
May I built an casio ex calculator using matlab as a beginner in my varsity project?
Is it possible to create a calculator app in MATLAB? Yes. Your level of skill with MATLAB will determine whether it's easy or difficult for you to create it.
If you're asking for permission to do so, that would depend on the person who's going to judge whether your varsity project meets their requirements.
Is it a wise decision?
That's something none of us can answer.
From where will I get sources
You'll have to write the code, of course. It is your varsity project, after all. The people on MATLAB Answers are generally willing to help when people have questions (and show what they've done up to that point where they encountered difficulty) but they're generally not going to simply write the code.
Since you said you're a beginner with MATLAB I suggest you start with the free MATLAB Onramp tutorial to quickly learn the essentials of MATLAB. Then work your way through the documentation on app building. I recommend using App Designer to develop your app.
