Survival analysis for several genes

Hi guys,
I wonder how can I do survival analysis for several genes at the same time.
I have the followup data of some patients(overall survival, disease-free survival), and i have the expression value of several genes (gene1, gene2, and gene3). To do survival analysis for one gene, I can divide the patients into two groups based on mean expression value of the gene and then analyze the survival data. But how can I analyze all the three genes at the same time ( I mean combine the expression of them, and consider them as one gene so I can group my patients).
Any response would be appreciated.
Thanks