Although Stored Process and Information Maps are both components of the SAS Enterprise Intelligence Platform, this forum is for stored process questions. Your best resource for help with Information Map questions is Tech Support. The method that you use (manually typing the CASE statement in the Expression Builder window or using the INSERT DATAITEM syntax) will vary depending on how you intend to create the Information Map. In addition, since your Information Map can reference Relational Tables or OLAP cubes, you would use MDX expressions for OLAP cubes. So the type of data will have an effect on what you want to do.
I have successfully typed a case statement in the Expression Builder Window of Information Map Studio. We teach the simple form of building expressions in chapter 3 of the Information Map Studio course. When you want to add an additional DATAITEM to an Information Map, you use an Expression Builder in Information Map Studio or the INSERT DATAITEM statement in PROC INFOMAP.
To send a question to Tech Support, go to http://support.sas.com/ and in the left-hand navigation pane, click on the link entitled "Submit a Problem".