copy, paste and loop

Good afternoon,
I need help copying from an offset column and then filling down. I know how many columns I have but the number of rows will vary so I can't set up a specific range.

My column names are A, B & C. As long as there is data in Column A, I need to copy the contents of cell B3 and paste it into cells C3, C4 and C5. But when the text in Column B changes, or when the first 8 digits in Column A change, I need the information in the adjacent B cell to be copied and pasted instead until the next change.

Please see the attached spreadsheet. I have given an example of what I have and what I want it to look like.
Thanks!