Another IF function problem

Hi

I have a table of 3000 individuals who have all valued 13 of 45 products. I need a way of assigning whether an individual gave product 41 a negative value.

So if individual 1 valued product 41 as negative I need a a way of placing a 1 next to all the procuts they valued, and if person 2 then valued 41 as positive I need to assign a 0 to all the procts they valued.

Have been trying IF functions but not sure on exactly how to do this.

Thanks in advance

JAmes