Drop 16 buttons on a calculator and label those buttons. If you're using Visual Basic (as opposed to Visual Basic.NET), you can create a "control array" and one event handler can handle all of the events. You can use the caption property to figure out what to do.
When one of the keys is pressed, you have to add a numeral to an "accumulator". This can be a text box on the form. So, if I press <1><2><3>, you'll want "123" to appear in the text box. This is simple stuff.
Finally, when a function key, "+", "-", "*", "/", you have to process it. Basically, you'll store the value in the accumulator text box into a hidden variable. You'll save the operation (the function key) so you'll know what to do when +, -, *, or / is hit again or when "=" is hit. You'll then allow the user to hit numeral keys to put a value into the "accumulator".
Start by putting the 16 buttons on the form and labeling them. Tell me what the labels are. Put a text box for a visible accumulator and create a variable for a hidden accumulator. Create an event handler for clicking the number keys. Make it so that when a number key is clicked, a numeral is added to the text box. When you get that done, put the source code in a ZIP file and attach it to a post here. (click the <Go Advanced> button. I'll coach you on handling the +, -, *, /, and = buttons.