Fotiman - 6:56 pm on May 22, 2012 (gmt 0)

The balance doesn't update until the page is refreshed.

That would seem to defeat the purpose of using AJAX then. :)
Another method for refreshing would be:
window.location = window.location;

However, if you know the "in" value, and you know the "out" value, couldn't you just update the balance using JavaScript instead of refreshing?

Also, one more bit of advice... mysql_escape_string has been deprecated and replaced with mysql_real_escape_string [php.net].