inventory report showing the ending balance of the previous month as the beginning balance of the current month

[Jenjus dela cruz]

I am in the process of making an inventory report using a pivot table. However, I have this problem of displaying the ending balance of the previous month as the beginning balance of the current month. Please help me solve this problem.
Here are the column fields of my data source: year, month, item, beginning balance, in, out, ending balance
My report is done monthly which shows the beginning balance which is the ending balance of the previous month, in, out, then the ending balance.