What is a "Scottish name" ?

Logically, what you are attempting cannot be done unless you are ceertain
that every surname beginning Mc or Mac that you are able to identify as
"Scottish"  should have the capitalisation you suggest, i.e.

McName
MacName

If it's obvious what the names ought to be, why not get it right in your
Excel file, then there's no problem anywhere else?

Peter Jamieson

The problem here is that there is no hard & fast rule. MacKenzie might be
spelled with an uppercase K, but Macintosh generally doesn't have any
capitalisation. Machin is a name that starts with Mac but isn't a "mac" name
and so is never capitalised. Macdonald can sometimes be MacDonald. Both
spellings come in the first 3 hits if you type "Macdonald" into Google.

There's a trick you can try out on people. Spell out the following names in
turn, and get them to try & pronounce them

M-A-C - D-U-F-F
M-A-C - D-O-N-A-L-D
M-A-C - H-I-N-E-R-Y

Unfortunately, this doesn't help you a lot. Without contacting the people
concerned, you can only make your best guesses as to the capitalisation of
their names. However, if you have only 8000 names, only a relatively small
proportion of those should be Mac names, so you should be able to check
those ones by hand. Don't forget also to deal with O' names, such as
O'Leary.