I have two checkboxes on a custom form, 'yes' and 'no'. I want to create
formula that says if neither yes or no is selected then a validation message
will appear asking for one of the boxes to be selected. This is how my
formula looks now:

Emergency Training CheckBox = yes
Emergency Training No CheckBox= no

IIf( [Emergency Training CheckBox] =false and [Emergency Training No
CheckBox ] =false , [Emergency Training CheckBox] or [Emergency Training No
CheckBox ] '' )