I need to do:

I am using the normal auto-fill function in Excel (double click the dot on the side of a cell) to copy the contents to the sub cells, so in this case clicking the dot in Cell A1 will do this:

I need a script that will repeat the process down the entire column, until there are no more values in the adjacent cell.
Presumably this is what you’re looking for:
That code with perform the following:
If you really want what’s in your screenshot, then you’ll need to do this:
Which does this: