Match and move the columns in Excel

Hi;

I have a sheet which has 4 columns ;

Column A and C have product numbers

Column B and D are for detail of the products.

What i'm trying to do is ; If a number in column A match with a number in column C then i want to take the value (product details) of B to column E. but if the number repeats then at second row and match again with that number in column C then i want to that the new value to column F.

It's a really particular problem for us. We are trying to create a new sql database for our new web page and we have to convert all data like this.

I tried it with =vlookup formula in Excel but it didn't work. i think this problem can solve only with macros. (If i'm not wrong...)

PS_ Please check the image, it's even hard to explain in my mother language.

Thanks