Doesn't show the UpdateProgress

[Guest]

HI!
In my web form I have one UpdatePanel with a GridView inside, one
UpdateProgress outside UpdatePanel, and one DropDownList outside UpdatePanel.
The DropDownList run as trigger of the UpdatePanel, so when the
selectedindexchanged event fires update the gridview. When the gridview is
updating, the operation takes a few seconds and I want to show the
updateProgress, but only appears when a gridview event occours.

How can I show the updateprogress for a updatepanel trigger?

Thanks