Private Sub Form_Load()
    On Error GoTo line1
    Open "c:\Lista.txt" For Input As #1
    Dim nombre As String
    While Not EOF(1)
        Line Input #1, nombre
        List1.AddItem nombre
    Wend
    Close
    Exit Sub
line1:
    MsgBox Err.Description, vbCritical, "Error " & Err.Number
End Sub

Private Sub Command1_Click()
    Dim i, V As Boolean
    For i = 0 To List1.ListCount - 1
        If UCase(Text1) = UCase(List1.List(i)) Then V = True
    Next
    If V = True Then
        MsgBox "El nombre '" & Text1 & "' aparece en la lista"
    Else
        MsgBox "'" & Text1 & "' no aparece en la lista"
    End If
End Sub