Multiple Searches

I am tring to do some code for item pricing. The code itself is not that important.  One thing I have come accross multiple times and can't find an answer to, is when I run more than one search in code. For example:

                            var recType = 'invoice';
                            var histCol = [];
                                histCol[0]= new nlobjSearchColumn('entity');
                                histCol[1]= new nlobjSearchColumn('item');
                                histCol[2]= new nlobjSearchColumn('amount');
                                histCol[3]= new nlobjSearchColumn('rate');
                                histCol[4]= new nlobjSearchColumn('recordtype');
                                histCol[5]= new nlobjSearchColumn('trandate');
                            var histFilter = [];
                                histFilter[0]= new nlobjSearchFilter('entity', null, 'is', custid);
                                histFilter[1]= new nlobjSearchFilter('item', null, 'is', itemId);
                                histFilter[2]= new nlobjSearchFilter('recordtype', null, 'is', recType);
                               
                            var histSearch = nlapiSearchRecord('transaction', null, histFilter, histCol);