Android app/widget to count days passed and calculate and than do simple math with the number

Hello, What I need is an android widget in which you the user is asked two thing: - the date on which a job started - the daily pay rate It then takes this two and calculates how much money you did until today. What I want from this is: the source code, small explication on how it was made where needed (not much), and explaination on how to put it on android market. This small app is the start on a larger project I want to make, a collection of apps that can be used to manage payment and calculate time spent on jobs for the industry I work in (offshore oil platforms) Please show me portfolio. Thanks, Andrei.