Calculated Column Count Rows Every Month

Hi I'm trying to create a calculated column to count rows per category (in my use case per month). 

The dataset has Date Dimension Table.

For example in the below picture I want a total count of the records per month and then per year. Let's assume the records come from a column called InternalID. I tried to do a distinctcount() but it didn't work. Basically I want to count the number of records where either Net Billed Time or Net Collected has a value, whether per month or year.