Average based on iif expression criteria

Hi this is my test code

create table #tmp1 (matter_ref int null
			,fee_earner varchar (10) null
			,dateclosed datetime null
			,value decimal null)	

insert into #tmp1 values ('12345','kerry','2013-12-10',9563.54)
insert into #tmp1 values ('12345','kerry','2013-12-10',null)	
insert into #tmp1 values ('12345','kerry','2013-12-10',null)
insert into #tmp1 values ('12345','kerry','2013-12-10',null)
insert into #tmp1 values ('12345','kerry','2013-12-10',null)
insert into #tmp1 values ('12345','kerry',null,null)
insert into #tmp1 values ('23456','kerry',null,900.00)

select matter_ref,fee_earner,dateclosed,value, row_number() over (partition by matter_ref order by value desc) as seq1
from #tmp1

drop table #tmp1

In SSRS I have set a matrix table with fee_earner in the row and value in the data section

To start I only want to bring back the value in the value column that meets this criteria

=IIF(not isnothing(Fields!dateclosed.Value) and Fields!seq1.Value = 1,Fields!value.Value,0)

this bring back the value 9564 which is the value I expect.

What I want to do is to average this value by how many records meet the above criteria which is one so the average would be 9564

but when using this =AVG(IIF(not isnothing(Fields!dateclosed.Value) and Fields!seq1.Value = 1,cint(Fields!value.Value),0)) I get 1366

It seems that it is averaging the 9564 by the 7 records.

How can I get around this?