Your best approach is to use an Inspector wrapper class so you can handle
click events individually for each open Inspector in case there's more than
one Inspector open. See Helmut Obertanner's C# Inspector wrapper at
www.outlookcode.com  for that.

Key points for the wrapper or other handling like that:

1. Use a unique Tag property for every toolbar you create so multiple open
items don't each get every Click event.

2. Create your UI using the Temporary argument and set it true so the UI is
automatically disposed of.

3. Delete the UI when the item is closed as a safety precaution and best
practice.