In a spreadsheet how do I keep a relative reference at a fixed offset to the current cell, fo example the cell three cells above the current one

I've seen a similar question regarding absolute references, How to keep a spreadsheet cell reference fixed when rows are inserted? and I think the solution may be similar.

I'm using a spreadsheet to do impedance calculations, and I want to be able to move, copy and paste blocks of formulae without breaking them. Each block takes its input from the four cells immediately above it. This MOSTLY works but breaks if I want to add or remove lines from the spreadsheet.

I'm looking for a way to say I want the cell N cells above the current one, and if I delete that line it will still reference the cell that is N cells above.

With a relative reference if the cell being referenced is deleted it becomes an invalid reference.