Simple Dialog Box Calculator With Insert

I am interested to know how to produce a dialog box that pops up upon a button press that does a simple calculation principal plus interest calculation.. ie.

the msg box or userform when called would have the following:

Label1 (Principal Amount) ===> Textbox1
Label2 (Interest rate per year) ====> Textbox2 (formatted to two decimal places).
Label3 (Results shown) ====>Textbox3

than an "ok" button on form or "submit" button when submitted, it is entered into a defined cell..


Just as an aside or complication, is it possible to have say after Label3 , 2 dropdown box where one reads colum values and one reads row values on the worksheet, that one people can pinpoint where to enter the final value from Label3