Help Needed to create DAX

Hi ,

I need your help to create a report. I have q requirement in which user will select an event then user will selected some static number between  to 3. For example, user has selected event number - 19 and then in second slicer user selected 2. So, i need to display total 3 lines in line graph which will show the attended participants month wise for event 19 (which selected from event slicer) and previous 2 events (number selected from second slicer). So my graph should have 3 lines (19,18,17). I have FactTable (Event Attended by Participants), EventEdition. Both tables having join (one to many) on ROW_ID from Event Table and Event Edition Wid from Fact Table and third tables contanis the static records(1,2,3) not having any join.

Can someone help to create a proper DAX? I have created below measure to get the result but it is giving only seleted event data.

# Unique Registered Contacts =

VAR MaxEvent = [Selected Event]

VAR MinEvent = MaxEvent - [Selected No of Events]

RETURN

IF(VALUES('Event Edition'[Event Edition])>= MinEvent && VALUES('Event Edition'[Event Edition]) <= MaxEvent,DISTINCTCOUNT( 'Fact-Registrations'[Contact Wid] ),BLANK())

Thanks in advance.

-S