The solution I finally decided to go with doesn't really solve the problem as I originally posed it, but has all the functionality I required. Instead of using a label, I attach a balloon widget to the listbox with a -postcommand option which updates the balloon text to reflect the number of elements in the listbox (and the number selected for good measure). Thanks for your help!

In reply to Re: binding Tk textvariables by Anonymous Monk
in thread binding Tk textvariables by Anonymous Monk

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