Stock Counting Month-by-Month

Hi all,

I am currently trying to build a stock report and I need a stacked column chart that shows month by month what we have in stock. In order for something to be counted as stock it needs to "WS" before the start of a month and "R" on or after the start of a month.

Currently, I have 48 individual calculations like this:

and I am wondering if there is a formula I could use to automate this so I don't have to do every month individually. 

I am hoping to get a final product that looks something like this:

but currently I am not sure if this is even possible due to the fcator of needing to filter each column for specfic dates. 

Please could anyone support me with this?

Thank you in advance for your help!