Col1=Range("Nom").Column
Col2=Range("Concat").Column
For i = 2 To Cells(Cells.Rows.Count, Col1).End(xlUp).Row 'Range("Nom" & Rows.Count).End(xlUp).Row
Cells(i,Col2) = cells(i,col1) & .....
'Range("Concat" & i) = Range("Nom" & i) & Range("Prénom" & i) & Range("Date_nai" & i)
Next