population list box without repeating information

ok, so i used the code below to fill a list box:

Private Sub UserForm_Initialize()

    Dim oIngredient As Ingredient
    Dim oIngredients As New Ingredients
    Dim avIngredients() As Variant
    Dim i As Integer
    
    For i = 1 To oIngredients.Count
        Set oIngredient = oIngredients.Item(i)
        avIngredients(i) = oIngredient.IngredientType
        If oIngredient.IngredientType= previoustype Then          ' need something here
            GoTo Skip
        Else
            Me.lstPreDefinedTypes.AddItem (CStr(oIngredient.IngredientType))
        End If
Skip:
    Next i
    
End Sub

well, not exactly; the "oIngredient.Type = previoustype" needs to be replaced with something that will look through the array being filled and return true if it finds a duplicate.
is there a way to do this?

thanks ahead of time,
sven