Get a reference to another form without creating new instance

Hi,

My Mdi Form contains a toolStripComboBox that contains a dataSource with a list of projects. Selecting a project creates an instance of a Project (child form). On closing the Project I need to clear the project name in  toolStripComboBox.  My question is how to get a reference to Mdi Form without creating a new instance of the form. I would appreciate if anyone can share an example.

Thanks,

wesley