How can you create and loop a column with the values of difference of columns in EXCEL VBA

I am new to Excel VBA and I need some help with code to create column with the difference between a column and a cell (A3) in a loop. So if you see in the picture I would for example like to know impact 1 with the H3 to a H.. = scenario(F3 to F...) - A3 and impact 2= Scenario2(G3...G)-A3 for x years (B3) for example.

How do you loop this? I started with an if loop but I struggled to loop the whole column for this.

Hopefully someone can I help me with this :)

photo of excel sheet