Set field values on beforeload user event script?

I'm trying to set a field on our sales order form to indicated whether or not the pick ticket has been printed for that particular order.  I've got that logic down and working with the following:

    if(type=='view'){
         var filters = new Array();
         filters[0] = new nlobjSearchFilter('internalid',null,'anyOf',nlapiGetRecordId());
         filters[1] = new nlobjSearchFilter('printedpickingticket',null,'is','T');
         filters[2] = new nlobjSearchFilter('mainline',null,'is','T');
        
         var rec = nlapiSearchRecord('salesorder',null,filters);

         // Hide the edit button when printedpickingticket for the record is set to True
         if(rec){
          form.removeButton('edit');
             }
       
However, what I also want to do, and I'm wondering about in general, is set a field value.  I thought you could do this on a before load user event script.  What I discovered in the netsuite help is that you can't set a field value for a custom field that stores it's value.  Is that really the case?  So basically, in order to do what I want with a check box field, I have to run the script every time the record is viewed, edited, etc...? It seems like there should be a more efficient way to do this?