Scrolling In Textarea To Selection In FF

I wrote a simple search function to find text in a textarea where not
all the text is visible (ie. the text box displays 10 lines but there
may be more than 1000 lines to search). I can find the text and select
it using the function below, BUT I can't figure out how to have the
textarea automatically scroll to the selection in Firefox. Any ideas or
suggestions?

function search(needle,haystack,start) {
var element = document.getElementById(haystack);
index = element.value.indexOf(needle,start);
element.setSelectionRange(index, index+needle.length);
}