Javascript to search backwards and forwards

Hi friends,
The following javascript code searches and highlights all occurances of searchedTerms in a page. But i need to use two buttons "next" and "previous". If i click on the "next" it should highlight only one searchTerm at once instead of all. Please anyone could help me to do this(FOR BOTH, "NEXT" and "PREVIOUS"). Please, it's urgent. Any reply will be appreciated.

function doHighlight(bodyText, searchTerm, highlightStartTag, highlightEndTag)
{
// the highlightStartTag and highlightEndTag parameters are optional
if ((!highlightStartTag) || (!highlightEndTag)) {
highlightStartTag = "<span name= 'highlighted_text' style='color:blue; background-color:yellow;'>";
highlightEndTag = "</span>";
}

// find all occurences of the search term in the given text,
// and add some "highlight" tags to them (we're not using a
// regular expression search, because we want to filter out
// matches that occur within HTML tags and script blocks, so
// we have to do a little extra validation)
var newText = "";
var i = -1;
var lcSearchTerm = searchTerm.toLowerCase();
var lcBodyText = bodyText.toLowerCase();

while (bodyText.length > 0) {
i = lcBodyText.indexOf(lcSearchTerm, i+1);
if (i < 0) {
newText += bodyText;
bodyText = "";
} else {
// skip anything inside an HTML tag
if (bodyText.lastIndexOf(">", i) >= bodyText.lastIndexOf("<", i)) {
// skip anything inside a <script> block
if (lcBodyText.lastIndexOf("/script>", i) >= lcBodyText.lastIndexOf("<script", i)) {
newText += bodyText.substring(0, i) + highlightStartTag + bodyText.substr(i, searchTerm.length) + highlightEndTag;
bodyText = bodyText.substr(i + searchTerm.length);
lcBodyText = bodyText.toLowerCase();
i = -1;
}
}
}
}

return newText;
}


/*
* This is sort of a wrapper function to the doHighlight function.
* It takes the searchText that you pass, optionally splits it into
* separate words, and transforms the text on the current web page.
* Only the "searchText" parameter is required; all other parameters
* are optional and can be omitted.
*/
function highlightSearchTerms(searchText, treatAsPhrase, warnOnFailure, highlightStartTag, highlightEndTag)
{
// if the treatAsPhrase parameter is true, then we should search for
// the entire phrase that was entered; otherwise, we will split the
// search string so that each word is searched for and highlighted
// individually
if (treatAsPhrase) {
searchArray = [searchText];
} else {
searchArray = searchText.split(" ");
}



var bodyText = document.body.innerHTML;
for (var i = 0; i < searchArray.length; i++) {
bodyText = doHighlight(bodyText, searchArray, highlightStartTag, highlightEndTag);
}

document.body.innerHTML = bodyText;
return true;
}


/*
* This displays a dialog box that allows a user to enter their own
* search terms to highlight on the page, and then passes the search
* text or phrase to the highlightSearchTerms function. All parameters
* are optional.
*/
function searchPrompt(defaultText, treatAsPhrase, textColor, bgColor)
{
// This function prompts the user for any words that should
// be highlighted on this web page
if (!defaultText) {
defaultText = "";
}

// we can optionally use our own highlight tag values
if ((!textColor) || (!bgColor)) {
highlightStartTag = "";
highlightEndTag = "";
} else {
highlightStartTag = "<span style='color:" + textColor + "; background-color:" + bgColor + ";'>";
highlightEndTag = "</span>";
}


/*if (treatAsPhrase) {
promptText = "Please enter the phrase you'd like to search for:";
} else {
promptText = "Please enter the words you'd like to search for:";
}*/


searchText =defaultText; //prompt(promptText);
return highlightSearchTerms(searchText, treatAsPhrase, true, highlightStartTag, highlightEndTag);
}


/*
* This function takes a referer/referrer string and parses it
* to determine if it contains any search terms. If it does, the
* search terms are passed to the highlightSearchTerms function
* so they can be highlighted on the current page.
*/
function highlightGoogleSearchTerms(referrer)
{
// This function has only been very lightly tested against
// typical Google search URLs. If you wanted the Google search
// terms to be automatically highlighted on a page, you could
// call the function in the onload event of your <body> tag,
// like this:
// <body onload='highlightGoogleSearchTerms(document.referrer);'>

//var referrer = document.referrer;
if (!referrer) {
return false;
}

}
function MyApp_RemoveAllHighlightsXml() {
SearchResultCount = 0;
bodyText = "";
var remove=document.getElementsByTagName("span");
if (remove) {
for (var i=remove.length-1;i>-1;i--) {
if (remove.getAttribute("name")=="highlighted_text") {
var s=remove.innerHTML;
var otxt=document.createTextNode(s)
remove.parentNode.insertBefore(otxt,remove);
remove.parentNode.removeChild (remove);
}
}
}
}