Have value in one cell equal a different value in next column

I'm still learning so I'm sure this is a relatively easy one, but I couldn't figure out how to word it properly to search for it.

Im trying to have a certain set of values in one column equal a price point in a different column.

EX: R2 = 100, R4=400, etc

When R2 is typed into a cell, if 100 could appear in the adjacent column.

I hope this makes sense. Thank you in advanced!