//Eg alert('x.asp'+'\n\n'+ChangeQueryStringValue('x.asp','Name','Peter Paul'));
//Eg alert(location.href+'\n\n'+ChangeQueryStringValue(location.href,'MoveTo','X.asp'));
function ChangeQueryStringValue(action,qsname,qsvalue)
{
	if (action.indexOf('?') == -1 )	 //If no querystring present
		return (action+"?"+qsname+"="+UrlEncode(qsvalue)); //x.asp?Name=Peter+Paul
	else
	{		
		if ( (action.indexOf("?"+qsname+"=") == -1 ) && (action.indexOf("&"+qsname+"=") == -1 ) )  //Passed querystring not already present		
		{
			return (action+"&"+qsname+"="+UrlEncode(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+UrlEncode(qsvalue));
			return newaction;
		}	
	}		
}


function UrlEncode(text) 
{		
	
	text=ReplaceAll(text, "?", "%3F");
	text=ReplaceAll(text, "=", "%3D");
	text=ReplaceAll(text, "&", "%26");
	text=ReplaceAll(text, " ", "+");
	text=ReplaceAll(text, ",", "%2c");	
	
	return text;
}


//Replace all given string from a string
function ReplaceAll(varb, replaceThis, replaceBy)
{	
	newvarbarray=varb.split(replaceThis);
	newvarb=newvarbarray.join(replaceBy);	
	return newvarb;
}