Previous from column to the left dax

HI

question

I'm looking for a dax formula that does the following

i have a pivot table that looks like this

customer number ,customer name ,Total bx sold
1234 jacks 53

Then i insert a slicer and i filter the total bx sold to the last 12 months

I would like to add another column that would give me total bx sold for the 12 months before the last 12 months

Any help is greatly appreciated