Retrieves an item from the DDE server.
DdeRequest( service, topic, item, format, resource )
Service is the name of the DDE-server.
Topic is the topic of the conversation.
Item is the data item for which the resource must be retrieved from the DDE server.
Format is the MS Windows data format of the item.
Resource is the resource that is set to the retrieved value.
NOTE: This method will not report that mandatory parameters are missing.