If data matches in one column, check 2nd column matches

I've been trying to figure this out for days, I'm sure it's possible but can't get it to work.

I have a set of data - in one column there are reference numbers. Sometimes the reference will only appear once, other times it will be duplicated.
Where a reference is duplicated, I want to check in the next column if the Name matches - I need to be able to identify the ones where the reference matches and the name doesn't, don't mind how it does it

In the example below, there are 3 columns of data and 5 rows...
The first row appears only once, so there is nothing to match - would prefer this to default to a Match.
The 2nd reference is duplicated, in row 2 & 3 and has matching names in column B so both of those should Match
In row 4, the reference is duplicated in row 5 however the names in 4 & 5 don't match.

12345 John
12346 John Match
12346 John Match
12347 John Doesn't match
12347 Jack Doesn't match

Hoping someone can help me with this!
Thanks in advance