HI,
As per my knowledge we cant do it in the workflow.
Please go through the following links,
http://leontribe.blogspot.in/2012/03/using-or-condition-in-workflows.html
https://msdynamicscrmblog.wordpress.com/tag/processes/
Thanks & Regards, MS CRM Consultant, V.Surya. My Blog: http://inventcrm.wordpress.com/