Custom Visual Studio SP2013 Workflow - Move Document(Current Item) into Document Set in another library (If no Doc Set exists, create first, then move)

First of all my apologies if this has already been asked and answered elsewhere, i have been trawling.

I have the task of creating a workflow that is triggered on a specific list upon a items field (ReferenceNumber) being populated. If so, then a if statement condition checks whether a doc set (under same reference number) within another library already exists. If so then move the file into it. If not, then create the doc set and then move the file into it.

Copying a document into another library location is fine, and even creating the doc set within that library is fine, but i'm falling short when I try and move the file into the document set. It gives me the option for the list, but unfortunately there is no further specifics.

I have read about the Copy Item Extended option within Designer, however there seems to be no details on adding this within 2013. Is anyone aware of anything related?

Can anyone lend a hand? Your time and efforts are truly appreciated.

Thanks.

Luke Hollinshead IT Technical Author / IT Analyst