Cell value in header

PS: If there is another way to do this, like reference a named section somehow from within the header, that's what the ^[Doc] was meant to be. But everything online points to VBA.

I would the page header to display some values from the workbook as values in the header.  I did google this and none of the results we're able to produce anything working. Not even any errors, the headers just stay blank.
So here is what I would like to be referenced:

And here is the VBA code I have been trying to make work. This is just the latest snippet I have worked with, Its been a few days of scouring the internet for something that will work. I am convinced it's my implementation that is incorrect. 

Function Author()
Author = ThisWorkbook.BuiltinDocumentProperties("Author")
End Function

Function Doc()
Doc = Worksheets("WorkInstructions").Range("D2").Value = ThisWorkbook.CustomDocumentProperties.Item("Doc").Value
End Function

Private Sub Workbook_BeforePrint(Cancel As Boolean)
Dim sTemp As String

With Worksheets("WorkInstructions")
sTemp = .Range("Z4").Text
PageSetup.LeftHeader = sTemp
End With
End Sub

Any input on this matter would be greatly appreciated, even if you don't think you have the answer. 🙂