I need to highlight duplicate cells in a column (not hide them). Someone
posted this simple solution a few weeks back:

"Assuming that A1 is a column heading and your name entries begin in A2,

1. select column A
2. data filter advanced filter check Unique Records Only click ok
3. Alt; (selects visible cells)
4. Data filter show all

Step 2 will hide all the duplicates.
Step 3 will highlight the remaining unique records.
Step 4 will make the entire column A reappear, with Unique Records
highlighted (grey) and the duplicates un-highlighted (white)."

My problem is Step 4 is not working. None of the cells are highlighted
(even though I know I have duplicates in my column). What am I doing wrong?

(I know how to highlight duplicates with a formula; but I would like to be
able to use this method too.)

I'll be grateful for any help.