Combining AND and OR logic

I'm trying to limit search results to only those whos dates are today or in the future. I created a flag field named current with a value of 1 to indicate those records which meet this criteria. I am doing a "google" style search where I pass the users search term into multiple fields, which works nicely, except for the AND and OR logic mix. Here's a sample of the PHP -

<?php

$search=new FX ($serverIP,$webCompanionPort);

$search->SetDBData('wkspweb.fp5','web');

$search->AddDBParam('current','1');

$search->AddDBParam('-lop','and');

$search->AddDBParam('description',$search_term);

$search->AddDBParam('-lop','or');

$search->AddDBParam('wksp_title',$search_term);

$search->AddDBParam('-lop','or');

$search->AddDBParam('presenter_first',$search_term);

$search->AddDBParam('-lop','or');

$search->AddDBParam('presenter_last',$search_term);

$searchResult=$search->FMFind();

?>

Is it possible to nest these queries somehow, or filter the results to exclude older events?