Move Ending Inventory to Following Month as Beginning Inventory

[#1]

I have a chart set up as a table that is a flow of product from Beginning Inventory, Shipments, Forecast, Cancels, Receipts, and Ending Inventory (see image).  I am trying to figure out how to take the Ending Inventory (Mar - Ending Inventory, which is a calculation) and put it in the Inv. Qty (Begining Inventory) for April. 

I cannot get my head around how to do this.  What I want to do is build in all of my planned receipts and forecast and be able to see what my monthly inventory looks like, both at the beginning of the month and the end.

Any ideas would be much appreciated.

Thanks,

Mike