Sorting options in select list doesn't work?

I have a dynamically populated selection box in an html form. I am able to move options between it and another select box. The array methods do not seem to work, however. Does anyone know why?

function sortonOptionText(arg1, arg2){
if (arg1.text < arg2.text)
return -1;
if (arg1.text > arg2.text)
return 1;
if (arg1.text == arg2.text)
return 0;
}

tbox.options.sort(sortonOptionText);

is not working. Thanks for your time.

jim