Unzip CSCustomFunctionWalkthrough.zip then open the WindwardCustomFunctions.sln in Visual Studio. 

In the Visual Studio Solution Explorer, select the file WindwardCustomFunctions.cs.

Paste this code after the last class MULTIPLYALL:

[FunctionDescription("Returns the common logarithm of the inputted parameter")]
public static double LOG(
[ParameterDescription("Take the common logarithm of this inputted number")] double num) 
//Note the use of [ParameterDescription(string)] which allows for custom tip information in AutoTag.
{
    return System.Math.Log10(num); //Returns the logarithm of the parameter.
}

Finally, click on Build, then select Rebuild Solution.

A notification in the Output pane indicates the build was successful. The build produced a DLL called WindwardCustomFunctions.dll.

To find the new WindwardCustomFunctions.dll file, in Solution Explorer right-click on the project, then select Open Folder in File Explorer.

In File Explorer navigate to WindwardCustomFunctions\bin\Debug\, and there is your new WindwardCustomFunctions.dll. Note this location for the custom function installation steps below.

1. In File Explorer navigate to the directory where your WindwardCustomFunctions.dll file is located (as shown above): "%USERPROFILE%\Downloads\CSCustomFunctionWalkthrough\WindwardCustomFunctions\bin\Debug"
2. Copy the file WindwardCustomFunctions.dll.
3. Next navigate to the install directory of the RESTful Engine, by default: "C:\inetpub\wwwroot\RESTfulEngine\bin."
4. Paste your WindwardCustomFunctions.dll into this directory.
   
   Starting In Version 21 also follow these steps
5. Open C:\inetpub\wwwroot\RESTfulEngine\web.config
6. Add the following under the <WindwardReports> in your "web.config" file
   <add key="function.files" value="C:\inetpub\wwwroot\RESTfulEngine\bin\WindwardCustomFunctions.dll"/>
7.  Save the "web.config" file

First, let's create an Out Tag:

• Close all open windows of Microsoft Office.
• Open Microsoft Word.
• Connect to a data source.
• Insert an Out Tag

Now, 

1. Select the Out Tag.
2. Click on the Equation button in the AutoTag Manager tab.
3. Choose "Custom" from the "Select a category:" pulldown menu.
4. You should see the new function LOG() in the "Select a function:" select list.