Random Response Fatigue Analysis cumulative damage.

Hello, 

is it possible  create at OptiStruct Random Response Fatigue Analysis with a cumulative damage for multi axis excitation and multi PSD profile?

For the moment I'm doing Random Response Fatigue Analysis with excitation axis by axis. But I would like to get combine result of damage from excitation X,Y and Z. I know how to do this at HyperLife but I'm not interesting  to use this method. I have to do at Optistruct 

Thanks in advanced