diff -r 52cb50cea1df -r b219134a2782 javaquery/demo-calculator-dynamic/src/main/java/org/apidesign/bck2brwsr/demo/calc/HistoryImpl.java
--- a/javaquery/demo-calculator-dynamic/src/main/java/org/apidesign/bck2brwsr/demo/calc/HistoryImpl.java	Sun Mar 31 12:26:07 2013 +0200
+++ b/javaquery/demo-calculator-dynamic/src/main/java/org/apidesign/bck2brwsr/demo/calc/HistoryImpl.java	Tue Apr 02 15:49:42 2013 +0200
@@ -19,6 +19,7 @@
 
 import org.apidesign.bck2brwsr.htmlpage.api.ComputedProperty;
 import org.apidesign.bck2brwsr.htmlpage.api.Model;
+import org.apidesign.bck2brwsr.htmlpage.api.OnFunction;
 import org.apidesign.bck2brwsr.htmlpage.api.Property;
 
 /**
@@ -34,4 +35,9 @@
     static String resultOf(String operation) {
         return "result of " + operation;
     }
+    
+    @OnFunction
+    static void twice(History data) {
+        data.setValue(2.0 * data.getValue());
+    }
 }