Index: src/gui/symbology-ng/qgsrulebasedrendererv2widget.cpp
===================================================================
--- src/gui/symbology-ng/qgsrulebasedrendererv2widget.cpp	(revision 14875)
+++ src/gui/symbology-ng/qgsrulebasedrendererv2widget.cpp	(working copy)
@@ -176,6 +176,7 @@
 #include "qgscategorizedsymbolrendererv2widget.h"
 #include "qgsgraduatedsymbolrendererv2.h"
 #include "qgsgraduatedsymbolrendererv2widget.h"
+#include "qgssearchquerybuilder.h"
 #include <QDialogButtonBox>
 #include <QInputDialog>
 
@@ -315,9 +316,19 @@
   l->addWidget( symbolSel );
   groupSymbol->setLayout( l );
 
+  connect( btnExpressionBuilder, SIGNAL( clicked() ), this, SLOT( buildExpreesion() ) );
   connect( btnTestFilter, SIGNAL( clicked() ), this, SLOT( testFilter() ) );
 }
 
+void QgsRendererRulePropsDialog::buildExpreesion()
+{
+  QgsSearchQueryBuilder dlg( mLayer, this );
+  dlg.setSearchString( editFilter->text() );
+
+  if ( dlg.exec() )
+    editFilter->setText( dlg.searchString() );
+}
+
 void QgsRendererRulePropsDialog::testFilter()
 {
   QgsSearchString filterParsed;
Index: src/gui/symbology-ng/qgsrulebasedrendererv2widget.h
===================================================================
--- src/gui/symbology-ng/qgsrulebasedrendererv2widget.h	(revision 14875)
+++ src/gui/symbology-ng/qgsrulebasedrendererv2widget.h	(working copy)
@@ -110,6 +110,7 @@
 
   public slots:
     void testFilter();
+	void buildExpreesion();
 
   protected:
     QgsRuleBasedRendererV2::Rule mRule;
Index: src/ui/qgsrendererrulepropsdialogbase.ui
===================================================================
--- src/ui/qgsrendererrulepropsdialogbase.ui	(revision 14875)
+++ src/ui/qgsrendererrulepropsdialogbase.ui	(working copy)
@@ -16,6 +16,9 @@
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
     <layout class="QHBoxLayout" name="horizontalLayout">
+     <property name="rightMargin">
+      <number>0</number>
+     </property>
      <item>
       <widget class="QLabel" name="label">
        <property name="text">
@@ -27,6 +30,19 @@
       <widget class="QLineEdit" name="editFilter"/>
      </item>
      <item>
+      <widget class="QPushButton" name="btnExpressionBuilder">
+       <property name="sizePolicy">
+        <sizepolicy hsizetype="Minimum" vsizetype="Fixed">
+         <horstretch>0</horstretch>
+         <verstretch>0</verstretch>
+        </sizepolicy>
+       </property>
+       <property name="text">
+        <string>Builder</string>
+       </property>
+      </widget>
+     </item>
+     <item>
       <widget class="QPushButton" name="btnTestFilter">
        <property name="text">
         <string>Test</string>