ontextchanged does not fire for custom Lookup in Ep Ax 2009

[paucer]

Vot problema:
<asp:TextBox ID="txtBoxItemId" runat="server" CssClass="AxInputField" AutoPostBack="True" ontextchanged="txtBoxItemId_TextChanged" ></asp:TextBox>

i cant get into txtBoxItemId_TextChanged() method, if i use custom lookup (based on web control),
if lookup is based on EDT or on dataset or custom dataset - then everything is ok, but those are too simple and can't meet the data selection requirements.
Somplex data retrieveing is made in lookup based on web control, selected value is returned to the txtBoxItemId, but that value cant be accessed in the page for further calculation. (previous value is accesed).
It seems like Autopstback/page_load does not work?
kto nibut' znajet vchiom tut delo?
Spasibo