// -------------------------------------------------------------------
// TabNext()
// Function to auto-tab through input fields, like phone or ssn, etc...
// Arguments    :
//   obj        : The input object (this)
//   event      : Either 'up' or 'down' depending on the keypress event
//   len        : Max length of field - tab when input reaches this length
//   next_field : input object to get focus after this one
// html code sample : 
//   <input type=text name="tab_1" size="3" maxlength="3" onKeyDown="TabNext(this,'down',3)" onKeyUp="TabNext(this,'up',3,this.form.tab_2)">
//   <input type=text name="tab_2" size="3" maxlength="3" onKeyDown="TabNext(this,'down',3)" onKeyUp="TabNext(this,'up',3,this.form.tab_3)">
//   <input type=text name="tab_3" size="4" maxlength="4">
// -------------------------------------------------------------------
var field_length=0;
function TabNext(obj,event,len,next_field) {
  if (event == "down") {
    field_length=obj.value.length;
  }
  else if (event == "up") {
    if (obj.value.length != field_length) {
      field_length=obj.value.length;
      if (field_length == len) {
        next_field.focus();
      }
    }
  }
}