Microsoft Excel 2002 and later versions of Excel provides a worksheet function that is named RealTimeData (RTD). The RealTimeData worksheet function permits you to call a Component Object Model (COM) Automation server for the purpose of retrieving data in real time. This article describes how you can use Microsoft Visual C++ to create a RealTimeData Server that you can use with the RTD function of Excel.

The VCRTDServer.exe sample contains a demonstration of a working RTD Server that is written in Visual C++. The sample runs on Microsoft Windows 98, Microsoft Windows Millennium Edition (Me), Microsoft Windows NT, Microsoft Windows 2000, Microsoft Windows XP, and on Intel platforms.

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The following file is available for download from the Microsoft Download Center:
Release Date: October 21, 2002

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base: Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.

The VCRTDServer.exe file contains the following files:

File name	Size
RTDServer.dsw	541 bytes
RTDServer.dsp	4909 bytes
RTDServerDLL.cpp	11168 bytes
RTDServerDLL.h	1265 bytes
RTDServerImpl.cpp	19560 bytes
RTDServerImpl.h	2701 bytes
RTDDataThread.cpp	3051 bytes
RTDDataThread.h	742 bytes
TList.h	6880 bytes
RTDServer.def	318 bytes
IRTDServer.idl	1937 bytes
Resource.h	455 bytes
Script.rc	1616 bytes
RTDServerSample.xls	30208 bytes

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Structure of a RealTimeData Server

The RTD worksheet function has the following syntax: The first argument, ProgID, represents the Programmatic Identifier (ProgID) of the RealTimeData server. The Server argument indicates the name of the computer on which the RealTimeData server is run. This argument can be a null string or can be omitted if the RealTimeData server is run locally. The remaining arguments represent parameters to send to the RealTimeData server. Each unique combination of these parameters represents one "topic", to which Excel assigns a unique TopicID. Parameters are case-sensitive. The following examples illustrate calls to the RTD server that result in three separate TopicIDs: For a COM Automation Server to be a RealTimeData Server that you can use with the RTD function of Excel, the COM Automation Server must implement the IRTDServer interface. The server must implement all the methods of IRTDServer:

ServerStart

STDMETHODIMP ServerStart(IRTDUpdateEvent *CallbackObject, long *pfRes)
				

ServerTerminate

STDMETHODIMP ServerTerminate(void)
				

ConnectData

STDMETHODIMP ConnectData(long TopicID, SAFEARRAY **Strings, VARIANT_BOOL *GetNewValues, VARIANT *pvarOut)
				

DisconnectData

STDMETHODIMP DisconnectData( long TopicID)
				

HeartBeat

STDMETHODIMP Heartbeat(long *pfRes)
				

RefreshData

STDMETHODIMP RefreshData( long *TopicCount, SAFEARRAY **parrayOut)
				

About the Sample RTD Server

The sample RTD server is a simple example of how an RTD Server that is written in Visual C++ may work. RTDServerDLL.cpp/.h contains the Class Factory and self-registration code for the RTD Server. RTDServerImpl.cpp/.h contains the implementation of the actual RTD Server. To make the IDispatch interface implementation easier, the RTD server uses the type information defined in IRTDServer.idl to delegate calls. This type information is a copy of the IRTDServer interfaces that are defined in the type library of ExcelXP. Because, in many cases, data for an RTD Server arrives asynchronously, RTDDataThread.cpp/.h defines a second thread that notifies Excel when new data is available.

Use the RTD Server in Excel

The "RTDServerSample.xls" Excel workbook that is included in the download contains RTD formulas that use the sample server. To use the sample workbook, you can rebuild and register the sample RTD server (by using Regsvr32.exe), and then open the Excel workbook.

Note When you use Microsoft Office Excel 2003 or Microsoft Excel 2002, make sure that the Macro security is set to Medium or to Low, or the RTD server cannot run.

If you prefer to create your own Excel workbook that uses the sample RTD server, follow these steps:

1.	Start a new workbook in Microsoft Excel.
2.	In cell A1, enter the following formula, and then press ENTER: =RTD("VCRTDServer.RTDFunctions",,"Hello") The return value is made up of the TopicID that is assigned by Excel and the current System Time.
3.	In cell A2, enter the following formula, and then press ENTER: =RTD("VCRTDServer.RTDFunctions",,"Hello") The initial return value matches the contents of cell A1 because this is the same "topic" that is used in A1.
4.	In cell A3, enter the following formula, and then press ENTER: =RTD("VCRTDServer.RTDFunctions",,ADDRESS(ROW(), COLUMN())) This formula uses the address of the cell to construct a unique topic string. You can copy and then paste this formula to as many cells as you want to see the unique TopicIDs assigned by Excel.

Note You must know the following information about the DisconnectData Event:

While Excel is a subscriber to your RTD server, Excel triggers the DisconnectData event when it no longer needs a topic (for example, when you delete or you clear an RTD formula in a cell). However, Excel does not call DisconnectData on each topic for the RTD server when the workbook is closed or when Excel quits. Instead, Excel calls only ServerTerminate. When you are creating an RTD server, you must code for any clean-up of topics or other objects when the ServerTerminate event fires.

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For additional information, click the following article numbers to view the articles in the Microsoft Knowledge Base:

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