I cannot see why you would want to do that. However if you do want to you
would probably create  a userform and then put text boxes on it. You would
need to code  the click event for each button to change the content of the box
you were using for the display.

If you are doing this simply as an exercise you will not gain knowledge
through asking others to do it for you. Start with what you know and ask on
the list if you get stuck on a particular issue.

If you need to do this as a business requirement please explain just what the
requirement is, and why the MS calculator  will not do. Also what you have
tried and what issues you have.

I would suggest you look at

http://www.catb.org/~esr/faqs/smart-questions.html

This article will give  you a valuable understanding into how forums work and
how to ask a question effectively.