Chart: Bar Series Masking

Hi,

I have a bar series, default loaded with 12 months data. I have combo box, where I can change my selection from 12 months to 6 months, 3 moths etc. When I change my selection from 12 months to 6 months, Rather than changing the Bar Series ItemsSource, I need to highlight the only 6 months data out of 12 months.

Please refer the attached screenshot where I have attached How 12/6 months Chart looks like