How do I Add a Profile Field Selector to the Homepage?

[davide101]

I have a column running down the right side of my forum homepage. I would like to have a profile variable that controls whether the user sees a 300px column or a 160px one. It's straightforward to create a variable and use a conditional to control this.

How do I let the user update the value from the right column of the homepage? I basically want a drop-down box that says "Narrow Layout" and "Wide Layout". When the user makes a selection, is there a way to use a Javascript onChange call to set the value? Or should I create a form that somehow reaches into the database and sets the value?

I really need guidance on the best way to approach this.

Please note that I don't want to use multiple styles to accomplish this. It leads to too much maintenance over the long run.