Custom KPI to give % of Month

I have a custom KPI scorecard that is giving us details of our custom table budget.

One of the custom KPI's I created was the % of the budget achieved for any of the date ranges in the scorecard.

As an example, we have 3000 tonnes of product budgeted for a month (custom KPI 1 created to pick up the budget amount), we have invoiced 1500 tonnes (custom KPI 2 to pick up the actuals recorded), 3rd KPI shows we have achieved 50% of the monthly budget (Used a formula percentage and divided the invoiced tonnes Custom KPI 2 by the Budget custom KPI 1).

I now need to create another KPI metric that will show what percentage of the month has passed as an additional comparison to the % of budget achieved. 50% of budget achieved if budget is 3000 T and we've invoiced 1500T but today is the 20th day of 31 days in the month, so we are 64% of the way through the month but only achieved 50% of budget.