If you are working on the Business Intelligence Platform, then I would recommend the SAS Add-in for Microsoft Office instead of DDE.
If you are working in EG with SAS on a server, you will frequently find the DDE methods do not work anyway, for example, there is no Excel on a Unix server that SAS on the server could talk to.
As for alternatives to DDE, many folks are currently using OLE-DB if they are doing .NET or ActiveX or VB types of processes.
But, depending on what you need/want to do, I generally recommend that you look at ODS MSOFFICE2K, ODS MSOFFICE2K_X, ODS TAGSETS.TABLEEDITOR and/or ODS TAGSETS.EXCELXP, as either HTML or XML based output that Excel can open and render.
The only downside of the ODS methods is that you cannot write to a single cell or range of cells in an existing worksheet with ODS -- ODS would make a new output file each time it is used. Only DDE (or ODBC or OLE-DB allow you to write to a particular cell location).