[texhax] Underline with numbers

[Evan Wessler]

I'm trying to create underlined text, but with numbers under the underlines. (I need to refer to the underlined pieces of text by number.) If that's confusing, imagine being able to do the same thing with an underline as you're able to do with an arrow like \xleftarrow[below]{above}, where the [below] and {above} text end up below and above the arrow with subscript/superscript sizing, respectively. 

Of course, I tried \underline[option]{text}, but was sad to discover no option existed.

Anyone have any advice?

Thanks!

E