Index: lang/en/filters.php
===================================================================
--- lang/en/filters.php	(revision 6195)
+++ lang/en/filters.php	(working copy)
@@ -74,6 +74,7 @@
 $string['profilelabelnovalue'] = '{$a->label}: {$a->profile} {$a->operator}';
 $string['removeall'] = 'Remove all filters';
 $string['removeselected'] = 'Remove selected';
+$string['replacefilters'] = 'Replace filters';
 $string['selectlabel'] = '{$a->label} {$a->operator} {$a->value}';
 $string['startswith'] = 'starts with';
 $string['tablenosave'] = 'Changes in table above are saved automatically.';
Index: user/filters/lib.php
===================================================================
--- user/filters/lib.php	(revision 6195)
+++ user/filters/lib.php	(working copy)
@@ -51,6 +51,9 @@
         // fist the new filter form
         $this->_addform = new user_add_filter_form($baseurl, array('fields'=>$this->_fields, 'extraparams'=>$extraparams));
         if ($adddata = $this->_addform->get_data()) {
+            if (!empty($adddata->replaceall)) {
+                $SESSION->user_filtering = array();
+            }
             foreach($this->_fields as $fname=>$field) {
                 $data = $field->check_data($adddata);
                 if ($data === false) {
Index: user/filters/user_filter_forms.php
===================================================================
--- user/filters/user_filter_forms.php	(revision 6195)
+++ user/filters/user_filter_forms.php	(working copy)
@@ -23,12 +23,28 @@
             }
         }
 
-        // Add button
-        $mform->addElement('submit', 'addfilter', get_string('addfilter','filters'));
+        // Add + replace filters buttons
+        $objs = array();
+        $objs[] = &$mform->createElement('submit', 'addfilter', get_string('addfilter','filters'));
+        $mform->addElement('group', 'addfiltergrp', '', $objs, ' ', false);
 
+
         // Don't use last advanced state
         $mform->setShowAdvanced(false);
     }
+    function definition_after_data() {
+        global $SESSION;
+
+        if (!empty($SESSION->user_filtering)) {
+            $mform       =& $this->_form;
+            $mform->removeElement('addfiltergrp');
+
+            $objs = array();
+            $objs[] = &$mform->createElement('submit', 'addfilter', get_string('addfilter','filters'));
+            $objs[] = &$mform->createElement('submit', 'replaceall', get_string('replacefilters','filters'));
+            $mform->addElement('group', 'addfiltergrp', '', $objs, ' ', false);
+        }
+    }
 }
 
 class user_active_filter_form extends moodleform {