Recognising and using decimal places

I have a question and answers widget that is to do with the hotel industry, so basically you get asked questions such as how many hotels, how many rooms etc and some of the questions such as how much does staff training cost is a number.
I would like to put in 250.00 as an amount and with all the other calculations I would liek that decimal place to be recognised and then in the final calculation that decimal point is displayed correctly, but it doesnt.
If there is a simple reason for this then great, but if you need screen schots, fla the action script then I can post that, but be great to have some help either way.

Thanks

Lee