No, there's not an API to do this. You'll have to implement your own solution.
The standard Palm OS GUI guidelines say that you should either hide controls that are useful with the current device configuration, or provide alerts that tell people why a button or control can't be used at the current time. A good example is the "Details" button in the To Do application. If you don't have a record highlighted, hitting "Details" will show an alert telling you that you need to highlight something for this action to have meaning. That lets a user learn about the UI of the app, rather than having to guess what he or she has to do to get a control to be enabled.
-- Ben Combee, DTS technical lead, PalmSource, Inc. "Combee on Palm OS" weblog: http://palmos.combee.net/ Palm OS Dev Fourm Archives: http://news.palmos.com/read/all_forums/
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