how to get Distinct Count CustomerID in a rolling 12 months window

[Anonymous]

Hi, I am fairly new to QV.

Searched up in the community, but didn't find something similar to my question.Can anyone help with the script in QV Script, not Expression. Thanks!

the input is

Person_ID	post_period
	1/31/2014
33993	2/28/2014
33993	3/31/2014
33993	4/30/2014
	5/31/2014
33993	6/30/2014
	7/31/2014
33993	8/31/2014
	9/30/2014 10/31/2014 11/30/2014 12/31/2014
231493	1/31/2015
231595	1/31/2015
231678	1/31/2015
231784	1/31/2015
231493	2/28/2015
231636	2/28/2015
231998	2/28/2015

Expected output is:

post_period	rolling12mos count Person_ID
1/31/2014
2/28/2014	1
3/31/2014	1
4/30/2014	1
5/31/2014	1
6/30/2014	1
7/31/2014	1
8/31/2014	1
9/30/2014	1
10/31/2014	1
11/30/2014	1
12/31/2014	1
1/31/2015	5
2/28/2015	7

Thanks!

[Anonymous]

exactly!