You would have to put your SUBJECT= variable in the MODEL statement, but this is likely to cause problems in the GEE fitting algorithm since that will add the need to estimate a parameter for each subject. Keep in mind that one of the main purposes and advantages of the GEE method is to avoid the need to estimate the possibly large number of subject parameters so that you can obtain good estimates and tests of the other effects in the model. The subject parameters are typically regarded as nuisance parameters with primary interest in the other parameters.  ... View more