I need to create a universal forecast measure that would take into account any interval set

[Sergii22]

There is a table with a plan for months. There is also a table with a fact by day. It is necessary to calculate the forecast for the end of the period, which is defined by the filter. Let's say there is a fact by day for January and a fact by day until February 7th. The time filter is set to January 1 - February 28. The formula for calculating the linear forecast that I use is: Fact for the month I clicked on/number of sale days * number of days in the month. Below pictures:

 

 

 

This is the same product that was sold in January and February.
Overhead bold cumulative sales on Feb. 7, followed by down January sales and February sales.
In the case of selecting sales for February, I received a correct forecast (green card). When choosing for January, in theory, I got a figure of what sales could be in terms of a linear forecast, but the period is already closed. The biggest problem is the result of the forecast when choosing total current sales. The formula considers an incorrect prediction.

Obviously, I need to create a condition that will evaluate the presence of the fact of a closed period (months) and calculate the forecast until the end of the current period. I need to create a universal measure that would take into account any interval set by the time filter.
The forecast measure, in my opinion, might look like this: Fact of the closed period + (Fact for the month I clicked on / number of sales days * number of days in the month.)
This is where I have a problem(
I would be very grateful for an example solution.