How to create a formula that will provide a quarter-to-date value?

Hey all,

I need a formula that will populate the QTD column with the appropriate value. For example, I need it to show the sum of December & January, if the current month is January.

Need the QTD column to show sum of Dec & Jan, given current month is January, etc.

My current formula isn't working, and I'm having a hard time thinking of a logical formula that will accomplish this. I have a reference table with various date information. I would like this formula to work whenever I change the current month cell to the current month-end.

Reference table for date selection. Formula should reference the current month - in this example, Jan. P2.

Any help is appreciated!