Modifying DCR content via Workflow

System

We are running TS 5.5.2

We have a simple Workflow. Author submits content. Editor Approves/Rejects it. If Approved, submitted to Staging, else Author is emailled and must review content.

I need to extend the Approve functionality. When a piece of content is approved, I need to write the name of the Approving Editor into the DCR file. The file contains an XML element called <Editor>, which is blank by default and this is the element I need to write to.

I have 2 questions:
1) How do I get hold of the name of the Editor?
2) How can I write the information to the DCR file?

I am very new to TS Workflow so all help will be most appreciated!

Thanks

Mark