An employee imports data (numerical values) into the range A1:T93 each
week. Some values are duplicated within the range, but because the
data is different each time, the values that are duplicated change from
week to week, and she has no easy way to determine which values are
duplicated or how often.

If a number appears in just 2 different cells, it's no problem. But if
a number appears in 3 or more cells, she needs to know that.

Is there some code that can run through the range to determine values
that appears in 3 or more cells and highlight them somehow (ideally
changing the background color of those cells).

As an example, if cells A6, B32 and M45 all contain the number 16, and
cells C9, F13, G83, H2 and R19 contain the number 32, she'd like the
background color of all 8 cells to be changed (say to yellow). (I used
16 and 32 as an example, but the numbers that are duplicated change
from week to week, and usually there are several different numbers
duplicated, not just 2.)

By the way, if finding those in 3 or more cells complicates things too
much vs. just finding those that appear in 2 or more cells, we can live
with that.

Many thanks.