Note that you'll be giving up significant speed if you start working off of a network drive versus your local HD.  Especially if the files are big, you are effectively reading and writing a large amount of data across your network.    Rather than a permanent setting, I would recommend using the user library option that @ksharp has recommended.   If you set up a library with the name user, SAS treats that as the WORK library instead of work, and you don't need to use a two level (libname.dataset) naming system. ... View more

First, if you have more than one record per customer / month, use the Summary Statistics task and summarize by customer and month, to get a total. Don't print the output, get an output dataset instead.   Once you have this, or starting with this if it's what you've got, you should have a dataset that looks like:   ID Month Demand a 01Jan2004 2525 a 01Feb2004 5566   . . .   a 01Dec2004 7345 b 01Jan2004 9866   . . .   b 01Dec2004 5324     Then you can use the Data | Transpose... task to create your output. Select ID as a Group variable, Demand as the Transpose variable, and Month as the "New Column Name" variable. ... View more