Combobox and Checkbox with Webservice

Hi

In below link, we can see combo-box with  checkbox.

http://demos.telerik.com/aspnet-ajax/combobox/examples/functionality/checkboxes/defaultcs.aspx

When Page load i will use loop to mark selected items like below

RadComboBoxItem item = ComboBox.FindItemByValue(myValue);
 if (item != null)
 {          item.Checked = true;          }

My Requirement:

Use ComboBox - Load on Demand Modes and use web service to load data

When Page load, how to show items initially (if it is a web service call)?

Can we do this? as in my project, i have userlist in drop down as webservice (normal combo box) and i need to change with combobox with checkbox functionality

Senthil