Please, advice a more elegant/correct approach to fill the column with values

Hello!

I have come up with a basic IF statement formula using OFFSETS to fill in values in the column.
But as a beginner, I am sure that my approach is not elegant, and can be improved. Could you, please, suggest better ways to do the same thing?

Short description, but it'll become clear once you see the example in the file.

I have a beginning value. I need to fill the column with alternating values, which:

- if the value above the current cell is negative, then add that negative value with the value in cell = current cell - 2;

- if the value above the current cell is positive, then take 25% of that positive value.

I came up with this formula: =IF(OFFSET(D7,-1,0)<0,OFFSET(D7,-2,0)+OFFSET(D7,-1,0),-OFFSET(D7,-1,0)*$B$1)

Thank you very much!