DatedIf formula with conditional formating and color coding

Hi,
I have a spreadsheet that gets added to every day. I want to figure out how many days it is from the "date of hearing" column to the "complete" column with the result in the "Days to complete" column. I used conditional formatting and a formula because I wanted the result to change color based on the result.
0 to 14 is green
15 to 30 is yellow
31 and above is red
I think I may have it right. If not, I welcome suggestions.
My question is how do I extend this conditional formatting down to the very last line of the column, line 1 million?
I want my lines to remain blank/white without a zero in them until the line is filled in.
I also have to copy this conditional formatting to multiple workbooks and can't seem to do that, too.

Any help would be welcomed.
Thanks in advance.
Lin

Yes You can achieve it

First select cell go to conditional formatting cell ->Highlight cell rules ->between , then enter 0 and 14 choose color Green
Repeat the step for 15-30

and for 31 choose ->Highlight cell rules ->Greater Than and color