The below snippet will provide you with a systems full user name.
Source Code
' @Author - Alexander Bolte
' @ChangeDate - 2014-10-13
' @Description - Returning the system user name.
Public Function getFullUserName() As String
Dim WSHnet As Object
Dim UserFullName As String
Dim userName As String
Dim UserDomain As String
Dim objUser As Object
Set WSHnet = CreateObject("WScript.Network")
userName = WSHnet.userName
UserDomain = WSHnet.UserDomain
Set objUser = GetObject("WinNT://" & UserDomain & "/" & userName & ",user")
UserFullName = objUser.FullName
Set WSHnet = Nothing
Set objUser = Nothing
getFullUserName = UserFullName
End Function
Referenced APIs
Since the source is using late binding it is not necessary to set a reference in the VBA Editor for a specific version of the referenced API named "WScript".