Large data set, pivot table and percentages

[bladewalker]

Hi,

I've been fiddling with this for a couple of hours but can't seem to get it the way I want it.
I have a large data set with thousands of records, structured like this:

Datetime	Status
2012-02-28 00:00	0
2012-02-28 00:10	1
2012-02-28 00:20	0
2012-02-28 00:30	1
2012-02-28 00:40	0
2012-02-28 00:50	1
2012-02-28 01:00	0
2012-02-28 01:10	1

Now what I'm trying to display is the following:

Monthly statistics of how big percentage of the month that Status has the value of 1.

I have been able to do this by creating a pivot table from the data set using the following settings:
Row labels:
Year, Timestamp, Status

Values:
"Number of" Status shown as "percentage of the row above"
(My translation here might not be perfect, I'm assuming you who excel at Excel understand what I'm talking about).

The problem here is that this also gives me the percentage of the status 0 - I don't need that information.
But since I need to include the rows with Status 0 in the pivot to get my percentage, I can't filter out this information before creating the pivot table.
The pivot table also shows how many percent of the records that belongs to each month - this is unwanted information aswell.

In short, I'd like to turn this:

Row labels	Number of Status
2012
jan	12%
0	5%
1	95%
feb	78%
0	25%
1	75%

Into this:

Row labels	Number of Status
2012
jan
1	95%
feb
1	75%

I don't know if I'm taking the the wrong approach to this?
I tried using calculated fields but there seems to be some rule I'm missing with those calculations because everything returns either 1 or ###...

Please, If someone has any tips for me in getting this to work I'd highly appreciate it!
Oh, and as you probably assumed this spreadsheet will be updated with new data automatically every once in a while, so I'm searching for a solution that involves as little manual fiddling with the setup as possible.