Budget Calculator

Hello folks, I'm trying to build a website where you can calculate your budget. I want it to have very simple interface where users be able to log in, input their income and expenses and store this info on database with timestamps, so users can look at their spending on a particular date. I have done some of the work already with joomla and build basic website interface with login and registration section. Everything i have done so far is working grand, but i'm having problems writing code for calculator mentioned above, that would talk to database and store every users calculations results. That's i'm looking for someone to do simple calculator code in either javascript or php of your choice, that would be intergrated into my existing webiste and talk with my already created database, that takes care of loggins. Here is a website i'm taliking about with all work i done so far www.YourExpenses.com. Contact me if you're are interested to help me. I know this is a very simple project for someone with the experience of using databases. I'll be waiting for your answer thank you. Kind Regards.