Help With Auto Calculations

Help With Auto Calculations

  
How can you set an application to make auto calcualtions. What I am needing to do is set a price of an object and set the intrest rate. Then I have an attrubite, Balance, that I would like it to store the calculation there, and I need it to be able to make the calculation every 7 days.
You can use a timer to compute ther value every seven days and store in the attribute. However I would recommend against storing computed values as it might me unnecessary. You can compute the value (with conditions) on the fly when needed.

Cheers

Ravi
OK, I understand the timer, but I don't understand how I might do the calculations. What I am needing to do is find the current balance from a loan. I also need to be able to subtract the payments that are made from another entity.