Clustering date ranges without overlapping. (Timeline bar chart)

[emorbidoni]

Hi, I'm stuck with this issue, please help!

I have a variable set of dates ranges, and I need to assign each range a number (or label) and avoid overlapped ranges in the same label.
So the numbers (or labels) will be the "Y-Series" for a timeline bar chart.

I need to get the minimum number of "labels" with no overlapped ragnges (3 in the case behind).

Explample of the set:

start date end date

04/2008	06/2008
04/2008	05/2008
07/2008	08/2018
07/2008	08/2008
09/2008	07/2014
08/2009	08/2009
08/2011	08/2011
12/2013	12/2013
02/2014	07/2014
09/2014	10/2014

<colgroup><col width="80" span="2" style="width:60pt"> </colgroup><tbody>
</tbody>

I need a formula to get the first column:

1	04/2008	06/2008
2	04/2008	05/2008
1	07/2008	08/2018
2	07/2008	08/2008
2	09/2008	07/2014
3	08/2009	08/2009
3	08/2011	08/2011
3	12/2013	12/2013
3	02/2014	07/2014
2	09/2014	10/2014

<colgroup><col width="80" span="3" style="width:60pt"> </colgroup><tbody>
</tbody>

Thanks!