COX Proportional Hazard Model with Time Dependent Covariate

Dear All, I have the following questions regarding with COX survial model with Time Dependent Covariate that needs your experience and expertise (1) Even we can do it with S-Plus or SAS, it can not be handled by NONMEM, am I right? If I am wrong, who has started the work? (2) How to make predictions with time-variant covariates based on COX model using S-plus or SAS, if not NONMEM? The question is asked because certain epidemic diseases are season-sensitive and none assumption on base hazard is advantageous over parametric approaches. Thank you in advance! Liang Zhao