Inside your MdiParent you will have a property, something like this:

public bool IsFormOpen
{
  get { return isFormOpenVariable; }
}

In your child you will do the following:

MyMdiParent parent = (MyMdiParent)this.MdiParent;
if( !parent.IsFormOpen )
{
  // whatever
}


/- Sam Judson : Wrox Technical Editor -/