Point to right certificate?

Just thinking how you might want to use this in the real world, and I think the following minor change may be required. Let me know

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The first macro, recalculates the certificates from the beginning each time, given the latest delivery.
The second will not recalculate if a vehicle has been and gone with the fuel and then more fuel comes in.

I'm soo sorry for a late respone, it's been a while. I appreciate any of your help.
Your code is working but not like i0ve been expected.
It's shows N/A rather than right value of fuel density.

1) Is it possible to enter date like eg. 28/5/22 when hit enter, vaule of that entered cell to be like d/m/y 13:45??
2) In the given file in #1 post, column A is of fuel delivery, and that column is edited manually

=ROUND(SUMPRODUCT(certs;amountoffuel)/SUM(amountoffuel;1) this would give a median for all, in formula range, certificates.
3) It is so inconvenient to me to enter date as d/m/y h:mm. Would be a lot easier to just hit 28/5 and enter, and there in cell to be like 28/5/22 13:45(current time). Not to use =NOW() 'cause it's volatile.

I could use a helper column to look up last couple of delivery rows(in range of a tank capacity, 100.000 litres), and then have a median value of certificates or to have a value of certificate of a greather amount of fuel delivery. Yeah, thats right. I need basic suproduct/sum calculation of last couple of delivery rows or some kind of "running total" to calculate median, then on base of that median, will give me a proximate value of which certificate to give to a customer.
Sorry for my weak english