microsoft.public.access

I am creating a report that shows products along with a subform
showing optional extras for each product. On the subform i have drawn
a box so it gives me the options when printed and packing the order to
tick them off as boxed. This work fine when i have optional extra but
when i have no optional extras in the subform i just end up with a box
on the screen which i do not want.

How do i set it up so it does not have box when i have no optinal extra