Computation Assistance

I know that I’m missing something really stupid, but I’d like to have help with this problem.

I have two input text fields and the correct entry for both text fields is MMM.CC, such as 721.80 and 554.60.

I have a formula which takes the first number and subtracts the second number, but it always leaves off the final zero, like in this situation it gives me 167.2 instead of 167.20. How can I ensure that it will give me the 0 in case the formula gives a result such as 167.20? I forgot that it is Action Script 2.0.