Outlook 2003 Word as Editor and .NET Forms

Our company has been working on an Outlook AddIn using VSTO which has a number of issues which we have not been able to resolve yet.
We would appreciate any insight or assistance you can offer.

Our .NET AddIn includes support for using Word as editor in Outlook 2003. On the editor window we add a custom command bar button that launches a .NET form. The problem is that the .NET form does not always appear in front of the inspector when Word is being used as the editor.
 
I have attempted to use the .NET methods and properties available on the Form (TopLevel, TopMost, BringToFront) to make it appear above the Outlook window but none of them were consistently working.

Is there any way I can ensure the .NET form comes out on top as our users are becoming frustrated with this? Thanks.

private void OnSendAndLogClick(Office.CommandBarButton Ctrl, ref bool CancelDefault)
{
 // Other code 
 using (FrmRegisterDMSEmail registerscreen = new FrmRegisterDMSEmail(_registerEmail))
 {                                                
  if (registerscreen.ShowDialog() == DialogResult.OK)
  {
                ...            
  }
 }
 // Other code
}

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