Apply formula to entire column macro

Hello,

I'm trying to make a macro that is applied to an active column permanently because people would be making adjustments by inserting additional rows at random locations which would throw off the calulations. The cell is referencing all the cells around it to see if it should execute. Currently it is being put in each cell locally, so row 1 is like:

=IF(C7="",I6,C7)

then row two is

=IF(C8="",I7,C8)