populate combobox from an excel sheet based on listbox selection (multiselect enabled)

I have a listbox with 3 values and multi select option enabled. Based on the values selected, I want to populate a combobox by referring to certain ranges in excel sheet. The code below works if only one value is selected from listbox. I know it will not work for multiple selections, but I am unable to write code to loop through the list of selections and then add corresponding ranges to combo box.

So, if I select customer1 and customer2, i want the values in ranges d3:d34 AND c4:c24 populated in the combobox. similarly for other combinations too. However, if one of the values is unselected, corresponding values should be cleared from the combobox.

If I were to save all the selected items in listbox in an array, how do i do a "search" or "find" for each of the values stored in the array?

Please suggest how I could revise this code.

Thank you!

Private Sub Combobox1_DropButtonClick()

    Dim curSelected As String
    Dim i As Integer

    For i = 0 To Listbox1.ListCount - 1
        If Listbox1.Selected(i) Then
            curSelected = Listbox1.List(i)
                If curSelected = "customer1" Then
                    ChooseDeals.List = Sheets("Sheet3").Range("d4:d34").Value
                ElseIf curSelected = "customer2" Then
                    ChooseDeals.List = Sheets("Sheet3").Range("c4:c24").Value
                ElseIf curSelected = "customer3" Then
                    ChooseDeals.List = Sheets("Sheet3").Range("e4:e20").Value
                End If
          End If
    Next i


End Sub