Finding a matching value in another range

I am trying to take a string from column B, find the match in column D, copy the corresponding value from Column C and past it into Column A and then go to the next row and repeat. Columns A and B correspond and columns C and D correspond. I wanted to use something like a vlookup but that will not work. I have a long set of IF statements for now but want to see if there is a function that can replace this. Any thoughts?