Simple Credits Remaining Program/Database

I need someone to create a form/database to do the following: Form has 4 fields: Username, Add Credits, Use Credits, Credits Remaining An administrator will be able to enter a username and add or subtract credits which will display the remaining credits. Example: Username: Freelancer101 Add Credits: 10 Administrator pushes the submit button: Credits Remaining: 10 Also, I would like it where the administrator can enter a username and push a button "Remaining Credits" and it displays the number of credits remaining.