Menambahkan Item Ke dalam ListBox tanpa Duplikat - VB6

Menggunakan fungsi API, sehingga kecepatannya bisa dikatakan sangat baik. Adapun kodenya adalah seperti di bawah ini:

Option Explicit 
 
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long 
Private Const LB_FINDSTRINGEXACT As Long = &H1A2 
 
Private Function AddItemListUnix(lst As ListBox, ByVal sItem As String) As Boolean 
    If (SendMessage(lst.hwnd, LB_FINDSTRINGEXACT, -1&, ByVal sItem) > -1) Then Exit Function 
     lst.AddItem sItem 
End Function 

Mengenai contoh penggunaannya:

Private Sub Command1_Click() 
    AddItemListUnix List1, "Test" 
    AddItemListUnix List1, "Test" 
    AddItemListUnix List1, "Form" 
    AddItemListUnix List1, "Test" 
    AddItemListUnix List1, "CommandButton" 
    AddItemListUnix List1, "CommandButton" 
End Sub