Duplicate data and concatenation

Hello,

I have a excel spreadsheet where I have 60,000 rows and columns are filled with data, column headers are Record Number, Last/Business Name, First Name, legal Business Name. the problem I am facing here is there are duplicates for example :-

Record Number, Last/Business Name, First Name, legal Business Name
555 ABC Company Harold
556 Smith Company Bill J
557 ABC Company Carol L

I have sorted according to name coz I have many duplicates and now the data shows this way

Record Number, Last/Business Name, First Name, legal Business Name
555 ABC Company Harold
557 ABC Company Carol L
556 Smith Company Bill J

My question is when there are duplicates in the Last/Nusiness Name column, I want to take the information that is in First Name and copy that into the Legal Business Name row. Once that is complete, then I want to remove duplicates.

For example,

Record Number, Last/Business Name, First Name, legal Business Name
555 ABC Company Harold Harold, Carol L
557 ABC Company Carol L _ Then this will be removed later with Remove duplicates
556 Smith Company Bill J

Basically copy the data from First Name column when a duplicate is found and make sure there are no duplicates, I cannot do this manually as its a huge file, Is there a Macro or a formula where I can work on. Please help!

Thanx!
DFX

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