Crawling with last line filter

I need help with calculation on last line, bit it must also recalculate with filters


Below is my code. it auto calculates and works out everything 100% i just have no clue how to get my total as aa calculated field that auto calculates when filter is added.

I need "F = (D-C)/D " on the last entry line.

here is my code below
I am currently trying below

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This calculate - but when I enter a filter it does not recalculate - How can i change this to only calculate active cell and add to last line