One way (Array-entered: CTRL-SHIFT-ENTER or cmd-RETURN):

=IF(C2=MAX(($A$2:$A$100=A2)*$C$2:$C$100),"Max","")

copy down.

Better (but not one of your options):

A Pivot Table with Unit in the Row field and Max of ODM in the Data
field.

In article ,
Erika wrote:

I have a sample of the spreadsheet that I am working with below, what I need
to do is put together a function or formula that will flag the column with
the highest ODM reading for each unit. Any ideas on a way that I could do
that - once the row was flagged on could filter to get the report that I want
- each unit listed with only the highest ODM.

unit Miles ODM
1 10 50000
1 20 40000
3 100 10
3 150 150
3 200 250000