diff --git a/client/src/main/java/ru/trader/model/support/BindingsHelper.java b/client/src/main/java/ru/trader/model/support/BindingsHelper.java
index 44d93a7..dcd0bb5 100644
--- a/client/src/main/java/ru/trader/model/support/BindingsHelper.java
+++ b/client/src/main/java/ru/trader/model/support/BindingsHelper.java
@@ -2,7 +2,9 @@ package ru.trader.model.support;
 
 import com.sun.javafx.collections.ImmutableObservableList;
 import javafx.beans.Observable;
+import javafx.beans.binding.DoubleBinding;
 import javafx.beans.binding.ListBinding;
+import javafx.beans.value.ObservableNumberValue;
 import javafx.collections.FXCollections;
 import javafx.collections.ListChangeListener;
 import javafx.collections.ObservableList;
@@ -12,6 +14,7 @@ import javafx.scene.control.TableView;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
+import java.util.function.BinaryOperator;
 import java.util.function.Function;
 
 public class BindingsHelper {
@@ -32,26 +35,30 @@ public class BindingsHelper {
         }
 
         return new ListBinding<T>() {
-            {
-                super.bind(list);
-                list.addListener((ListChangeListener<T>) c -> {
-                    while (c.next()) {
-                            if (c.wasAdded())
-                                for (T item : c.getRemoved()) {
-                                    super.bind(item);
-                            } else if (c.wasRemoved()){
-                                for (T item : c.getAddedSubList()) {
-                                    super.unbind(item);
-                            }
+            private final ListChangeListener<T> listListener = c -> {
+                while (c.next()) {
+                    if (c.wasAdded())
+                        for (T item : c.getAddedSubList()) {
+                            super.bind(item);
+                        } else if (c.wasRemoved()){
+                        for (T item : c.getRemoved()) {
+                            super.unbind(item);
                         }
                     }
-                });
+                }
+            };
+
+            {
+                super.bind(list);
+                list.addListener(listListener);
+                list.forEach(super::bind);
 
             }
 
             @Override
             public void dispose() {
-                list.forEach((v) -> super.unbind(v));
+                list.forEach(super::unbind);
+                list.removeListener(listListener);
                 super.unbind(list);
             }
 
@@ -83,4 +90,64 @@ public class BindingsHelper {
         table.setItems(sList);
         sList.comparatorProperty().bind(table.comparatorProperty());
     }
+
+    public static <T> DoubleBinding group(final BinaryOperator<Double> operation, final Function<T, ObservableNumberValue> convert, final List<T> list){
+        if ((list == null)) {
+            throw new NullPointerException("Operands cannot be null.");
+        }
+
+        return new DoubleBinding(){
+            private final ListChangeListener<T> listListener = c -> {
+                while (c.next()) {
+                    if (c.wasAdded())
+                        for (T item : c.getAddedSubList()) {
+                            super.bind(convert.apply(item));
+                    } else if (c.wasRemoved()){
+                        for (T item : c.getRemoved()) {
+                            super.unbind(convert.apply(item));
+                        }
+                    }
+                }
+            };
+
+            {
+                if (list instanceof ObservableList){
+                    ObservableList<T> oList = (ObservableList<T>) list;
+                    super.bind(oList);
+                    oList.addListener(listListener);
+                }
+                list.forEach(v -> super.bind(convert.apply(v)));
+            }
+
+            @Override
+            public void dispose() {
+                list.forEach(v -> super.unbind(convert.apply(v)));
+                if (list instanceof ObservableList){
+                    ObservableList<T> oList = (ObservableList<T>) list;
+                    oList.removeListener(listListener);
+                    super.unbind(oList);
+                }
+            }
+
+            @Override
+            protected double computeValue() {
+                double res = 0;
+                for (T item : list) {
+                    res = operation.apply(res, convert.apply(item).doubleValue());
+                }
+                return res;
+            }
+
+            @Override
+            public javafx.collections.ObservableList<?> getDependencies() {
+                ArrayList<Observable> dependencies = new ArrayList<>(list.size());
+                list.forEach(v -> dependencies.add(convert.apply(v)));
+                if (list instanceof ObservableList){
+                    dependencies.add((ObservableList)list);
+                }
+                return new ImmutableObservableList<>((Observable[]) dependencies.toArray());
+            }
+        };
+    }
+
 }