Analyzing .cdf files with no .cel files

Hi I am trying to process Affymetrix data in Matlab. All I have for the experiment is .cdf files (one for each sample). In the past I was able to analyze this in Genespring, without any other file types. For Matlab, it is unclear if this is possible. I am a little confused by what is in the .cdf file, as in some cases it seems to have all the info you need, whereas in other it seems that at .cel file is needed. Thanks Bryan