Disable the action in PopupMenus extension point?

[jayjamba]

Hi All,
I have made one popupMenu to be displayed in one view through "org.eclipse.ui.popupMenus" extension point. In that I have added one action which will be displayed as a menu item in the context/popup menu generated in that view.
Now what i want is..to disable one specific action dynamically based on some condition. I am able to access the menu through menu manager class and also got the menu item but when i m using setEnabled(false) method on it, It is not reflecting any change.. i mean it is not getting disabled..

If there is some alternate way to disable the action of popupMenu, dynamically... than..plzz reply...

Thanks & Regards,
Jay.