Calculating an average tax rate

[proben930]

I am trying to make a form that will take a number typed into a text box, and calculate the applicable taxes. The rate changes every year, and the information is stored in a table (beginning date, end date, int rate for that year). It would involve for say 3/21/02, calculating 365 - that date and multiplying by that years rate, adding 2003 * 2003 rate, etc.. just like regular taxes are calculated. Any ideas? I am stumped

 

[proben930]

Allow me to be a little more clear....

-Customer owes x amount of money, which is due at a certain time
-for the amount of time past that day, customer is charged interest
-need to calculate interest due

Its easy but, problem is the interest rate we use changes frequently. And if they are say 65 days late, you would prorate the tax (65/365 * int rate). The interest rates are stored in a table. I'm not a programmer but I am fairly intelligent when it comes to this stuff.. even a hint as to where to start would be helpful

 

[neileg]

Lookup Year() to find out which rate is applicable.
Lookup YearFrac() to calculate what proportion of the year is involved.

While you could do this in code in your form, I would suggest that it would be easier to do this in a query, and bind your form to the query.