If then Else formula at webi report

Hi,

here's my scenario.

I need to create a report based on Open SAP notifications. Now, Notifications can be open if notification can be open if one or more tasks within the notification is still not completed and Notification can still be open if all the tasks within Notifications are completed but overall Notification is still open.

My report requirement is like this,

I need to show notification number along with person responsible for the task. person responsible for task, if any of the task within notification is open then their name should appear against the notification like notification 2 but if all the tasks are completed for the notification then the last name of the person responsible should appear against the notification like notif 1 and 3.

I used the following formula but it did not give me the required result.

=If(IsNull([Query 1].[Date on Which the Task Was Completed])) Then [Person Responsible for Task (Partner Number)] Else (Last([Person Responsible for Task (Partner Number)]))

this formula does work somewhat as it does bring partial result. if notification had more then 1 task open it only brings the 1st person responsible for the open task and it does not bring any other person responsible however if there are no open task then it does bring the last person responsible.

is there a way to achive my desired result?

thanks,

BIAPP