Help for select an item in popup button


I want to select an item (whose title is “x”) in a popup button.

I tried something like :

select (menu item  of menu of popup button "myPopup" of window "myWindow" whose title = "x")

It seems to be false.

What is the right code to select an item with its title and with its index?

Thanks for help.

Model: iMac II
Browser: Safari 417.8
Operating System: Mac OS X (10.4)

Thanks Jacques, that all right!