vba macro code error: statement invalide outside type block

I just started working with macros and the vba code. I have read online how to do what I want but when I run the code i get an error "statement invalid outside type block". Here is my code:

Private Sub Worksheet_Change(ByVal Target As Range)

If Not Intersect(Target, Range("C9:C11")) Is Nothing Then
    'Do nothing if more than one cell is changed or content deleted
    If Target.Cells.Count > 1 Or IsEmpty(Target) Then Exit Sub
            If (C9 = "x" Or c10 = "x" Or c11 = "x") Then
            'display error message
            MsgBox("You can only select 1 yes for this category", vbOKOnly, "Error") As VbMsgBoxResult
            End If              
    
    End If
End If
End Sub

Maybe it has to do with my msgBox it highlights the top line in yellow, but the msgBox is highlighted in blue. Any help would be great! Thanks

There were a couple of issues that you need to watch for.

1. When using the worksheet change event, you should toggle enable events
2. If you are going to reference a range like C9 then you have to explicitly call it as a range:
   

   If Range("C9") = "X" then...

Does the following help?

Private Sub Worksheet_Change(ByVal Target As Range)

    Application.EnableEvents = False
    If Not Intersect(Target, Range("C9:C11")) Is Nothing Then
        'Do nothing if more than one cell is changed or content deleted
        If Target.Cells.Count > 1 Or IsEmpty(Target) Then Exit Sub
            If (Range("C9").Value = "x" Or Range("c10").Value = "x" Or Range("c11").Value = "x") Then
                'display error message
                MsgBox "You can only select 1 yes for this category", vbOKOnly, "Error" ''As VbMsgBoxResult
            End If
    End If
    Application.EnableEvents = True
End Sub