Line Item Won't Add After Validation

I've written a script to validate line items based on the value of a custom field within the main tab of a sales order record. The validation works when the item is listed in the code. However, when an item should be able to be added, nothing happens. I click the add button in the UI and a new line item is not activated on the sales order.

I'm thinking maybe my return statements are not correct somehow? Any help is appreciated

Here is my code:

function validateLine_rec() {     var stRecord = nlapiGetRecordType();     if (stRecord == 'salesorder') {    var stProgram = nlapiGetFieldValue('custbody64');    var stItemId = nlapiGetCurrentLineItemValue('item', 'item');      if (stProgram == '2') {     if (stItemId == '24' || stItemId == '25' || stItemId == '26') {      alert('You can not use this item for Classbook Orders');      alert('stProgram = ' + stProgram);      alert('stItemId = ' + stItemId);      return false;     }     return true;    }   }  }