thank you both Lynn and Sean - I appreciate your patience.

below is a more detail - i wanted to try to keep it simple but apparently i over-simplified the first time!

select reg.CUSTOMER_ID, jh.join_date,

case when jh.join_date BETWEEN DATEADD(mi,-45,web.START_DATE_TIME) and web.END_DATE_TIME then 'Attended Webinar'

else 'Did Not Attend Webinar' end as AttendedWebinar

from Webinar.Registration reg

INNER JOIN Webinar.Webinars web ON web.PRODUCT_CODE = reg.PRODUCT_CODE

inner join dbo.CUSTOMER cus on cus.MASTER_CUSTOMER_ID = reg.CUSTOMER_ID

left outer join Webinar.JoinHistory jh on jh.WEBINAR_HOST_REGISTRATION_ID = reg.WEBINAR_HOST_REGISTRATION_ID

where reg.REGISTRATION_TYPE = 'LIVE'

and reg.PRODUCT_CODE = @WebinarID

and (@ReportType = case when jh.join_date BETWEEN DATEADD(mi,-45,web.START_DATE_TIME) and web.END_DATE_TIME then 'Attended Webinar' else 'Did Not Attend Webinar' end

or

@ReportType = 'All Webinar Registrants')

the problem i have is reflected in the below result set:

CUSTOMER_IDJOIN_DATEAttendedWebinar

0000000330644/17/2013 4:28:18 PMDid Not Attend

0000000330644/18/2013 9:40:59 AMAttended

The result i need is either Attended or Did Not Attend, and i realize my query is working correctly as written - it needs to be tweaked to allow for one or the other.