Index: calculatorview/src/sans/perspectives/calculator/calculator.py
===================================================================
--- calculatorview/src/sans/perspectives/calculator/calculator.py	(revision 306219c16148ce09126b839f2e16a7e5c71587a7)
+++ calculatorview/src/sans/perspectives/calculator/calculator.py	(revision ce3feca1e7d2324618e496e9578a205a745f3d33)
@@ -52,4 +52,6 @@
         Returns a set of menu entries for tools
         """
+        data_oper_help = "Perform arithmetic data operation (+...) "
+        data_oper_help += "and combination (|)"
         kiessig_help = "Approximately computes the "
         kiessig_help += "thickness of a shell or the size of "
@@ -65,5 +67,5 @@
         #data_editor_help = "Meta Data Editor"
         return [("Data Operation", 
-                        'Data operation', self.on_data_operation),
+                        data_oper_help, self.on_data_operation),
                 ("SLD Calculator", sld_help, self.on_calculate_sld),
                 ("Density/Volume Calculator", mass_volume_help, 
Index: calculatorview/src/sans/perspectives/calculator/help_panel.py
===================================================================
--- calculatorview/src/sans/perspectives/calculator/help_panel.py	(revision 992b59494b89bebf0b1f4655ca7e3c5623c428dd)
+++ calculatorview/src/sans/perspectives/calculator/help_panel.py	(revision ce3feca1e7d2324618e496e9578a205a745f3d33)
@@ -64,4 +64,6 @@
             <body>
             <ul>
+            <li><a href ="data_operator_help.html" 
+            target ="showframe">Data Operator</a><br></li>
             <li><a href ="sld_calculator_help.html" 
             target ="showframe">SLD Calculator</a><br></li>
Index: calculatorview/src/sans/perspectives/calculator/media/data_operator_help.html
===================================================================
--- calculatorview/src/sans/perspectives/calculator/media/data_operator_help.html	(revision ce3feca1e7d2324618e496e9578a205a745f3d33)
+++ calculatorview/src/sans/perspectives/calculator/media/data_operator_help.html	(revision ce3feca1e7d2324618e496e9578a205a745f3d33)
@@ -0,0 +1,35 @@
+<html>
+<body>
+<h4>Data Operator</h4>
+<ul>
+<li><a href="#Description">Description</a></li>
+<li><a href="#Howto">Howto?</a></li>
+</ul>
+<h5><a name="Description">Description</a></h5>
+<p>
+This dialog panel provides arithmetic operations between two data sets (the last data set could be a number): <br> 
+When the data1 and data2 are selected, their x (or qx and qy for 2D) values must match with each other.
+</p>
+
+<h5><a name="Howto">Howto?</a></h5>
+<p>
+1) Type the data name resulted from an operation.<br>
+2) Select a data/theory in the drop down menus. When the data2 is set to number,
+ type a number in the text control box. <br>
+3) Select an arithmetic operator symbol; + (for addition), - (for subtraction), 
+* (for multiplication), / (for division), and | (for combination of two data sets).
+If two data sets are not match, the operation will fail and the background 
+color of the combo box items will turn to red (WIN only).<br>
+4) If the operation is successful, hit the Apply button to make the new data.
+Then the data name will be shown up in the data box in the data explorer.<br>
+Note: The errors and warnings will be displayed at the bottom of the SansView window. 
+</p> 
+<p>
+<img src="data_oper_pic.png">
+<br>
+Data operation dialog
+</p>
+
+</body>
+
+</html>
Index: fittingview/src/sans/perspectives/fitting/media/model_editor_help.html
===================================================================
--- fittingview/src/sans/perspectives/fitting/media/model_editor_help.html	(revision 66798ce8b98699100512fbd93f0066a446607eb3)
+++ fittingview/src/sans/perspectives/fitting/media/model_editor_help.html	(revision ce3feca1e7d2324618e496e9578a205a745f3d33)
@@ -5,5 +5,5 @@
 <li><a href="#description">Description</a></li>
 <li><a href="#new">New</a></li>
-<li><a href="#sum">Sum(p1,p2)</a></li>
+<li><a href="#sum">Sum|Multi(p1,p2)</a></li>
 <li><a href="#advanced">Advanced</a></li>
 <li><a href="#delete">Delete</a></li>
@@ -28,9 +28,10 @@
 <br/>
 <br/>
-<h5><a name="sum">Sum(p1,p2)</a></h5>
+<h5><a name="sum">Sum|Multi(p1,p2)</a></h5>
 <p>
-This option create a new sum model. Fill up the (sum model function) name and the description. 
+This option create a new sum (or multiplication) model. Fill up the (sum model function) name and the description. 
 The description will show up on details button in the application.
-Then select the p1 or p2 model for the sum model (Note: Not all models are currently supported), and click the Apply button for activation. 
+Then select the p1 or p2 model for the sum/multi model, 
+select an operator as necessary and click the Apply button for activation. 
 Hit the 'Close' button when it's done.
 </p>
