// JScript

function ChangeQueryStringValue(qsname,qsvalue)
{
    var action = window.location.href;
    if (action.indexOf('?') == -1 )	 //If no querystring present
        return (action+"?"+qsname+"="+qsvalue); //x.asp?Name=Peter+Paul
    else
    {		
        if ( (action.indexOf("?"+qsname+"=") == -1 ) && (action.indexOf("&"+qsname+"=") == -1 ) ) //Passed querystring not already present		
        {
            return (action+"&"+qsname+"="+qsvalue); //x.asp?Age=25&Name=Peter+Paul;
        }
        else //Passed Querystring already present, replace it no matter if it is ?Name= or &Name=
        {
            var replaceQSPrefix=(action.indexOf("?"+qsname+"=")==-1)?"&"+qsname+"=":"?"+qsname+"=";
            var replaceQSSuffix=""; //This will be John in case of ?Name=John or &Name=John 
            startpos=action.indexOf(replaceQSPrefix);
			
            for (a=(startpos+replaceQSPrefix.length);a<action.length;a++)
            {
                if ( action.charAt(a)=='&' ) //Next querystring beginning
                    break;
                else
                    replaceQSSuffix += action.charAt(a);
            }
            newaction=action.replace(replaceQSPrefix+replaceQSSuffix,replaceQSPrefix+qsvalue);
            return newaction;
        }	
    }		
}