John,
In mine the fromclass calls the form manager's KillForm method from the Destroy. The Killform method does two things it does an ADEL of the row for the form (based on the Tag passed from the form and then redimensions the array, and it NULLs out the Form property which is used by the from manager as a direct reference to the currently active form. The form class' Activate event calls the form manager to "register" the form as the active form and passes its tag value. The form manager RegisterForm method just puts the object reference into the Form property.