Highlight substring in element

What is the best way to highlight a specific substring in a div element in an event? By highlight, I mean apply some CSS style, like yellow background or something.

Basically I need a simple JS client side function of the form:

function (element, start, end) { 
  // element is the element to manipulate.  a div or span will do
  // start and end are the start and end positions within the text of that
  // element where highlighting should be.
  // do the stuff
}

Only one highlight will be active.