PLEASE HELP!!!!! SOS!

I need to make changes to simple product custom options to have an ability to choose only one check box out of 2,3 or more options and to replace price value accordingly. As you can see on my product page, customer can choose both options or one of them or none of them. My goal is to make him an option to choose ether none of them, or only on out of two or 3. Example is clearly found here:

http://www.comfyco.com/store/leather...ts/jmsoho.html

As you can see, you we can only choose either “sofa” or “loveseat” check box, and if you choose one, the other automatically unchecks.

Also, the price is being replaced, but not added or subtracted (no +$...... or $-..... signs).

And as you can mention, product name right below these options - changes from “Soho Loveseat” to “soho sofa”, depending on which box is checked.

I am very new to magento, please help me if anyone has some spare time. I would appreciate any kind of help in figuring out what needs to be done.

I don’t post my own web site url, because it’s really default and all default magento product options available.

SIncerely, Tim