[AccessD] Key Preview Problem

Hi all,
This is probably a simple problem, but I can't find the answer in Help or several books:
I have a form to enter Delivery Tickets.  The data can take several avenues as to how it is billed, so I use Option Groups to get that info, and then I make certain blocks visible or not visible.  If I close the form and re-open, the option groups will have neither option selected.  But if I use the Control to Enter a New Ticket, the option that was last used is still checked.  
In the "Enter New Ticket" control (Properties or code) can I tell access to uncheck the options.  Setting the "No Default" property doesn't do it.

TIA,

Jim