Can anyone help with a creating a 'Pop Up' box?

Question

Hi there,
Was wondering if anyone could help me with some javascript in my shopping cart. I have two things that I'm after but the second one might be too hard?
1. I need a pop up box saying "Please choose a shipping option" when they click on the 'Get Quote button' as it's not a mandatory field for quoting.
2. I'd love to have a pop up box in the shopping cart that won't let a customer proceed to getting quoted if their purchase is below $250.
Our quote button is "Charge to Franchise" and the website is www.harcourtsonlineshop.co.nz
Would love your help! I'm only able to do very basic things in BC.
Thanks for your time,
Kirsty

Answer 1

Alright... first off this only almost works.  I'm posting it because hopefully one of the js gurus around here can figure out what the issue is because I can't.
For me at least (testing in greasemonkey) it works fine until I make more than a couple changes in the shipping options menu, after which it just stops altogether.
You'll need jquery running obviously.
var tooltip = '';     
var total = $('tr.total').find('td:eq(2) > strong ').text();
total = parseFloat(total.replace(/[^0-9\.]+/g,""));
var unlockcharge = 250.00;
var t='';
$('body').append(tooltip);
function setPageState(){
     $('#tooltip').empty();
     t='';
     sel = $('select#ShippingOptions').val();
     var bt = (total < unlockcharge)? true: false;
     var ps = (sel == -1)? true: false;
     if(bt){
          t+='A minimum purchase of $250 is required for a quote.';
     if(ps){
          t+= 'Please select a shipping option.';
     if(bt||ps){
          $('#tooltip').html(t);
          $('#catshopquote').fadeTo(100, 0.5).on({
               'click': function(e){
                    e.preventDefault();
          $('#catshopquote').on({
               'mouseenter': function(e){
                    $('#tooltip').css({
                         'top': (e.pageY-15)+'px',
                         'left':e.pageX+15+'px'
                    }).fadeIn();
               'mouseleave': function(e){
                    $('#tooltip').fadeOut();
$('select#ShippingOptions').on('change', function(){
     setPageState();
setPageState();