Make clicked button go bold and other choices go gray

Hello,

I posted a question here about three years ago and was totally blown away by the higher form of intelligence which resides here.

On to the current problem. I am trying to design a slick, user-friendly form using buttons. In each section, there might be 3-6 buttons. There are probaly a dozen sections. When the user opens the form, I would like all the buttons to be black font. When the user clicks one of the buttons, the button will go to bold (i.e. light my button), and the other 2-4 buttons will all automatically go to a light gray. Visually, the users will know where they are in the form. I would like for the buttons they have chose to really stand out. If they want to change their minds, they can still go and click one of the gray buttons, and then the gray button will go to bold and all the other buttons in that section will go to gray.

If someone could explain to me how to do this with one row of buttons, I think I can figure out how to apply the same formula to the whole form.

In other words: A1 shows "100" B1 shows "50" and C1 shows "25". If user selects B1, then "50" is bold and A1 "100" and C1 "25" go light gray. By choosing B1, the number 50 shows up to the right, say G1. I can handle it from there.

Please Obi-wan, you're my only hope!

Much thanks,
John