Workflow to Auto populate the Lookup field

Hi Folks ,

    I am using CRM 2013 , I have entities called Events, Leads and Members . In the Event entity i have lookup fields for leads and Members. Now the problem is when i enter the email address in Event Entity . the lead lookup field or Member lookup field should Auto populate  once the email address match with lead record Email Address or Member Email Address .For this Scenario i created a workflow , but it is not working 

Here is the conditions of workflow 

  If Event  (Email Address) equals to  Lead (Email Address), then

  Update  Event  Lead field with {lead(event)}

Other Wise  If Event (Email Address ) equals to Member (Email Address), then 

Update  Event   Member Field with {lead(member)}

Can Anyone help me to achieve this so i can track all the activities and events occurred for each record in Lead and Member 

Thanks In Advance,