Suitescript - How to ONLY Run on "Create" not "edit

Hi everyone - I am using the following code to reallocate orders to the location where the correct stock is available, and if no location has available falling back to location '8'.

However - There are times when we need to override the system and choose a specific location - with the below script in place - it undoes out changes.  How can I set this to ONLY run on Creation of a new order, and not on editing an existing one?

// BEGIN CUSTOM FUNCTIONS FOR SETTING LOCATIONS FOR WEB ORDERS  // This custom function is run immediately before a sales order is saved.     function customBeforeSubmit()  {   debug('Before Submit is called');   return chooseLocation();  }  //END CUSTOM FUNCTIONS FOR SETTING LOCATION  //BEGIN LOCATION  function chooseLocation()  {  // Get entire quantities of all inventoried items in the sales order. Note that optional filtering  // criteria is used when calling the getItemMap() function to exclude noninventory items.  var itemMap = getItemMap('NonInvtPart');  var numLines = nlapiGetLineItemCount('item');  var goodLocations = new Array();  var badLocations = new Array();  // Get available quantities for each location of each