When i select a month previous 3 months data should be shown

[#1]

Hi my data is like this

Month            products

Dec 2015         10

Nov 2015           3

Oct 2015             1

Sep 2015           3

Aug 2015           6

Jun   2015         15

My requirement is when i select a month say Dec 2015, dec2015 data + the previous 3 months data sholud appear. If i selected oct 2015 i want oct2015 and previous 3 months data

Regards

Jhon

[#2]

Can you please help me out