Count readings at level in hiararchy

I want to be able to count the number of readings that are at each level of hiararchy.

Like I have data saved up at 15 minutes granuality level.

So

1:00

1:15

1:30

1:45

And my time dimension has minute, hour, day and monthly and yearly hiararchies.

What I want to be able to get is how many total records are there at montly, or hourly levels

So if I am at the hourly level,  I should have a count of 4 for time starting at 1 am till 2 am. I should have 3 for time starting at 1:15 to 2 am.

I tried doing this but it returns 1 to be which isnt correct.

count(DESCENDANTS ([Dim_DateTime].[HourofDay].currentMember))

if currentmember is 1, it should return me 4 count.

Please help.

Thanks

-Sarah