DDE (Dynamic Data Exchange) is a well-established mechanism for exchanging data among processes in MS-Windows. There are three DDE commands for establishing communication with Windows programs such as Excel. Which of these commands you use depends on how you plan to control the flow of data between the spreadsheet and the DataHub instance.
DDEPoke writes a data value to the DataHub program. For example, to send a value from an Excel spreadsheet to a DataHub instance, the DDEPoke command is run from within an Excel macro. For more details, please refer to Section 19.2.2, “Method 2 - Writing Excel macros that use the DDEPoke command”.
DDERequest reads a data value from the DataHub program. To get that value into Excel, for example, the DDERequest command is run from within an Excel macro. For more details, please refer to Section 19.1.2, “Method 2 - Excel Macros using DDERequest”.
DDEAdvise creates a connection, called an advise loop, that updates a new data value automatically. The advise loop is a unidirectional link, established by a client program that wants to receive data from a server program. The client continues to receive new point values as long as the two programs are running, or until the advise loop is terminated.
You can use DDEAdvise to read data from a DataHub instance by configuring it to act as a DDE Server. For an example using Excel, please refer to Section 19.1.1, “Method 1 - Drag and Drop using DDEAdvise”.
Likewise, you can use DDEAdvise to write data to a DataHub instance, by configuring it to act as a DDE Client. For an example using Excel, please refer to Section 19.2.1, “Method 1 - Configuring DDEAdvise loops in the DataHub instance”.
For more information on DDE, please refer to Appendix 7, DDE Overview.