floppy drive not ready

I have a  DriveComboBox control  which generates an exception (inouterror
#21) when I select an empty floppy drive.  I can't locate an event in the
control where I can trap for this exception using a 'try/except' block, and
my process for putting a default exception in the application isn't working.
There has to be an easy you to do something so simple.  I'm using Delphi 3.
Any help would be greatly appreciated.

PM Doyle