Global variables in Power BI

Hi All,

I have a report which contains 'Date' slicer.

I want to create 2 variables which will store the Date values for last month and month before last values based on slicer selection.

For example, if user selects 1 March 2017, then the 2 variables should have values as 1 February 2017 and 1 January 2017 respectively. 

Once I have these 2 date values I need to update the header text of table columns.

Please let me know of how I can achieve this.

Thanks in advance.

Regards,

Vinayak