Chi Square Distributions -- TI 89

We're learning about problems like the ones below in my stat class right now, but my professor has no idea how to use a TI 89, so I'm usually stuck in class. Would anyone know how to solve the following problems using Stat List Editor on a TI 89? - You randomly pick and weigh 30 samples of an allergy medication. The sample standard deviation is 1.2 milligrams. Assume the weights are normally distributed, and construct 99% confidence intervals for the pop. variance and standard deviation.
- Find the critical values for chi square right tail and chi square left tail