It actually uses a XML-based catalog system. Practically, data is stored in specific XML files (Core.SC2Mod, Liberty.SC2Mod and LibertyMulti.SC2Mod - core files + one belonging to the custom map). You can of course import the files into Microsoft Excel and then perform various manipulations on the resulting spreadsheet (through VBA scripts, for instance).
I personally prefer the XML-parsing & manipulation in a stand-alone programming IDE (such as Java - NetBeans/Eclipse or C#/VB - .NET) than introducing the spreadsheet as an intermediary data container to be manipulated by VBA scripts, but to each their own.
Good luck!