Find and replace by row, for multiple rows with individual values.

Explaining concisely as possible, I have several hundred rows of product data for new product lists I am creating.

To create new products, I have duplicated a single product from the first row for the entire sheet.

In my first column I have my product code for each of my new products, in the following columns there are several instances of my original product code, which is duplicated down each row.

Currently, I am highlighting each row, and finding the data D300 and performing a 'replace all' with my new product code from column A.

The selecting the next row, with the find and replace window still open, but changing the 'replace with' value to the next product code.

I have attached a sample sheet and tried to give an idea of the context of the information as the 'D300' value does not always feature as solitary information in the cell.

Does anyone know, if there is a function that can be copied from 1 row to the next, or another way of simplifying this process?

(1 method I am trying is to record a macro, however because there appears to be no function in 'find and replace' to select the contents of a cell as the 'replace with value', this method is not working.)