Add unique items in Listbox based on Combobox

Try

Dim c As Range, Variance As String, dic As Object
Set dic = CreateOjbect("Scripting.Dictionary")
dic.CompareMode = 1
ListBox1.Clear
With Range("Order_list")
    Set c = .Find(Me.ComboBox1, LookIn:=xlValues)
    If Not c Is Nothing Then
        Variance = c.Address
        Do
            dic(c.Offset(0, 1).Value) = Empty
            Set c = .FindNext(c)
        Loop While c.Address <> Variance
        ListBox1.List = dic.keys
    End If
End With