insert formulas based off changing reference cells

Hi,

i need a macro which puts the formulas into the cells as per attached.

the number of rows between the "beam" can be variable
the number next to the beam will be variable.
the number of "beam" rows is vaiable

my thoughts where to do a find"beam" and refernce the cells address the create formulas off those points but dont have the skill to code this

any help would be appreciated
beam macro.xlsx

thanks
Ross