Multiselect dropdown - selected/checked values

SmartClient : Smartclient v8.2p_2012-06-07 - Power Edition

Browser : IE 9

I am using Dynamicform field with following properties,

name: "inqList",
ID: "trdField",
editorType:"select",
multiple:true,
optionDataSource: "inqDS",
multipleAppearance: "picklist",
displayField:"username",
valueField:"userId"

This shows the dropdown with values from datasource where user can make multiple selection by clicking on checkbox.

I am storing user selection in session and when I reload the above component , I want to set the earlier user selection as checked/selected on the dropdown.

Can you please let me know how can i achieve this?

I basically want to load the multiselect dropdown with some values marked selected/checked.

Please help.