Looking for help in vba to solve Sumproduct with condition

I want you to help me with this problem. i want the sumproduct of one row as integer with another which has a value for each weight. example,
x: 2, 2, 3, 2,
y: 45, 53, 64, 85.
of which the weight of
y: are 2, 2.5, 3, 4.
from
= if(y1>79,4,if(y2>69,3.5,.......)) in VBA