Hi Trey,
Make that parameter to Optional prompt, to make optional prompt in the paremeter you need to change the properties of parameter as Optional prompt as "true".
with the optional prompt if you specify 'yes' it will display those vales, if 'NO' it will display those values, if you didn't specify any values then it will display all values.
the formula is look like the below
if (HasValue({?OpenToPublic}) = "Both" then true
else if {?OpenToPublic} = 'Yes' then {rpt_DriveMaster.OpenToPublic} = True
else if {?OpenToPublic} = 'No' then {rpt_DriveMaster.OpenToPublic} = False
Hope the above information will help you.
--Naga.
