[![enter image description here](https://i.stack.imgur.com/FX8Ef.png)](https://i.stack.imgur.com/FX8Ef.png)I have an issue I cannot seem to wrap me head around using SQL Server. I have a forecast amount which is done at a monthly level. I need a query that would calculate the remaining forecast based on the day I run the query. I was trying with `DATEPART`, `DATEADD`, & `DATEDIFF`but had no luck. Anybody have a way they have found to do something similar? 

Thanks!