Using UserName in Select Case

I have a macro, code below, which fires when the workbook is opened. It checks to see if the username is written in column A of Sheet2; if it is, it writes the date beside it. If it isn't, it writes the username in the next open cell in column A, puts the date beside it, saves itself, then displays a timed messag of my choosing.

Right now I can put the UserName (StrUser) in my message, but I want to personalize it more by putting the actual name (User) in the message, and I'm trying it with a Select Case routine, but it's not working. I always plugs in "I don't know who you are", though I've verified my StrUser name is correct. I'd appreciate it if anyone can point out my problem in the code below. BTW, the "Sheet1.Select" statements are because I want my users to only be looking at sheet1.

Thanks.

Option Explicit
Private Sub Workbook_Open()

    Dim strUser As String, lrow As Long
    strUser = Environ("username")
    Dim cell As Range
    Dim User As String
    

Application.ScreenUpdating = False
Sheet1.Select
    
' check to see if the file was opened in readonly mode, if so exit sub
    If Me.ReadOnly = True Then Exit Sub
        
' can write and save changes - not read only
With Sheets("Sheet2")
        ' can write and save changes - not read only
        For Each cell In .UsedRange
            If cell.Value = strUser Then
                cell.Offset(0, 1).Value = Date
                Exit Sub ' username is present
            End If
        Next cell
    
       With .Cells(.Rows.Count, "A").End(xlUp).Offset(1, 0)
            .Value = strUser
            .Offset(0, 1).Value = Date
        End With
  
       Select Case Cells(Rows.Count, 1).End(xlUp).Text

          Case "LUPOREJ"
            
             User = "John"

          'Case "IDUNNO"

              'User = "Somebody else"
        
          Case Else

              User = "I don't know who you are."

    End Select
    End With
    Me.Save 'save now to capture username in log
       Sheet1.Select
        CreateObject("WScript.Shell").Popup "Hello" & User & " This is a first attempt at a messaging system within Excel for specific worksheets." & vbCrLf & "This workbook will close itself after 7 seconds, which should be enough time to read this message." & vbCrLf & "If I've done it right you should not see this msgbox again.  Thanks for trying it.", 7, "This Msgbox will close itself."
        'Run "Msgbox_Test()"
            
           
           
   Application.ScreenUpdating = True
   

End Sub