I'm excited to share that I've found what I was looking for!
I'm posting it as it may help somebody else.
So I took a few steps back and read in detail all the labels in the "Custom Fields" dialog in MS Proj. I've digged MSDN about the terms that made sense to me, such as LookupTable and OutlineCodes. I was pushing the wrong button! The code below illustrates this.
Sub TestGOC()
'pfonseca Sep 2013
'This Sub exhausts my Immediate Window. Run with caution (or dont run at all)
Exit Sub ' safety plug
For i = 1 To Application.GlobalOutlineCodes.Count
Debug.Print "GOC" & "(" & i & ")" & " " & Application.GlobalOutlineCodes(i).Name
For j = 1 To Application.GlobalOutlineCodes(i).LookupTable.Count
Debug.Print "..." & "(" & j & ")" & " " & Application.GlobalOutlineCodes(i).LookupTable(j).Name
Next j
Next i
End Sub
The function below dumps the allowed values per CEF received. It's a starting point for more elaborated use-cases:
Sub DumpListValues(pCEFName As String)
'pfonseca Sep 2013
For i = 1 To Application.GlobalOutlineCodes.Count
If Application.GlobalOutlineCodes(i).Name = Trim(pCEFName) Then
For j = 1 To Application.GlobalOutlineCodes(i).LookupTable.Count
Debug.Print "(" & j & ")" & " " & Application.GlobalOutlineCodes(i).LookupTable(j).Name
Next j
End If
Next i
End Sub
The same issue as posted in MSDN.
Pedro