Controls TextBox - Setting to read-only

Description: Sets a TextBox to read-only, prohibiting alteration to content
' set text1 to multi-line

'Const WM_USER = &H400
'Const EM_SETREADONLY = (WM_USER + 31)
'Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
(ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Long) As Long

Open "C:\CONFIG.SYS" For Input As #1
While Not EOF(1)
     Line Input #1, TmpStr$
KeepStr$ = KeepStr$ & TmpStr$ & Chr$(13) & Chr$(10)
Wend
text1.Text = KeepStr$
' Set the text box to read-only mode:
ret& = SendMessage(text1.hWnd, EM_SETREADONLY, True, 0&)
If ret& = 0 Then MsgBox "Couldn't Set Text Box to Read-Only."