var custom = false;
			var first_name = false;
			var last_name = false;
			var invoice = false;

			jQuery(document).ready(function() {
				validate();
				jQuery('#usernameStatus').html('');
				jQuery('#custom').keyup(function() {
					if (jQuery('#custom').val().length)
						custom = true;
					else
						custom = false;

					validate();
				});
				jQuery('#first_name').keyup(function() {
					if (jQuery('#first_name').val().length)
						first_name = true;
					else
						first_name = false;

					validate();
				});
				jQuery('#last_name').keyup(function() {
					if (jQuery('#last_name').val().length)
						last_name = true;
					else
						last_name = false;

					validate();
				});
				jQuery('#invoice').blur(function() {
					if (jQuery('#invoice').val().length && !jQuery('#invoice').val().match("[^A-Za-z0-9]")) {
						jQuery('#usernameStatus').html('<img src="/mgl/accounts_setup/indicator.gif" align="absmiddle" />&nbsp;Checking availability...');
						jQuery.post("/mgl/accounts_setup/check_username.php", {
								username: jQuery('#invoice').val()
							},
							function(response) {
								jQuery('#usernameStatus').fadeOut();
								setTimeout(function () {
									if (response == 'true') {
										jQuery('#usernameStatus').html('&nbsp;<img src="/mgl/accounts_setup/cross.png" align="absmiddle" />');
										invoice = false;
										validate();
									}
									else {
										jQuery('#usernameStatus').html('&nbsp;<img src="/mgl/accounts_setup/tick.png" align="absmiddle" />');
										invoice = true;
										validate();
									}
									jQuery('#usernameStatus').fadeIn();
								}, 400);
							}
						);
					}
					else {
						jQuery('#usernameStatus').html('&nbsp;<img src="/mgl/accounts_setup/cross.png" align="absmiddle" />');
						invoice = false;
						validate();
					}
				});
			});

			function validate() {
				jQuery('#susubmit').attr("disabled", true);
				if (custom && first_name && last_name && invoice) jQuery('#susubmit').attr("disabled", false);
			}