Assessing Soap header values inside orchstration

I am using biztalk 2006 R2. I am publishing an orchstration as webserice(.asmx). I have soap header authentication. I am accessing the webservice with soap header credentials. But  I need to access another webservice from orchestration which also takes same soap header values. I need to pass the soap header values to the webservce for authentication. I need to know how can I access the soap header values in the orchestration (message assignment shape)