Since you can have other To recipients besides the one the check box adds, you'll probably find it easiest to handle this in the Item_Send event handler. Note the syntax for referring to a control using the page and control names:
Function Item_Send()
Set myPage = Item.GetInspector.ModifiedFormPages("Name of your customized page")
Set CheckBox1 = myPage.Controls("CheckBox1")
If CheckBox1.Value = True Then
Set recip = Item.Recipients.Add "name_of_recipient"
recip.Resolve
End If
End Function
--
Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
and Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers