Can someone tell how to disable and item in a UltraExplorerBar thoruhg code?
I'm afraid I don't understand your question. You can access any UltraExplorerBarItem from the Items collection of the group to which it belongs. You can also (for example) get a reference to the item at the cursor position using the ItemFromPoint method. Once you have the reference, you just have to set the Settings.Enabled property to false to disable it.
What I am asking for is how to disable and enable a single item when there are several items to choose from. Any ideas?
Set UltraExplorerBarItem.Settings.Enabled to false.