userform combobox2 does not have unique values and will not fill listbox

Try this version to see if it does what you're looking for.

UserForm1?

Option Explicit

Private dic As Object

Private Sub UserForm_Initialize()
    Dim a, i As Long
    Set dic = CreateObject("Scripting.Dictionary")
    dic.CompareMode = 1
    a = Sheets("sheet1").Cells(1).CurrentRegion.Resize(, 2).Value
    For i = 2 To UBound(a, 1)
        If Not dic.exists(a(i, 1)) Then
            Set dic(a(i, 1)) = _
            CreateObject("Scripting.Dictionary")
            dic(a(i, 1)).CompareMode = 1
        End If
        dic(a(i, 1))(a(i, 2)) = Empty
    Next
    Me.ComboBox1.List = dic.keys
End Sub

Private Sub ComboBox1_Change()
    With Me
        .ComboBox2.Clear
        If .ComboBox1.ListIndex > -1 Then
            .ComboBox2.List = dic(.ComboBox1.Value).keys
        End If
    End With
 End Sub

hi jindon
thankyou for sending info have got 2 codes looks different slightly so can have good play with them ,works well
many thanks colin

hi wher
excellent work many thanks does nearly exactly what I would like ,but would like to have the option of just using location then find to see all and the way you have coded it too,will have to try and dicepher the code you sent
many thanks colin