Hi

Welcome to board!

not sure, but does this make any good ?

Code:
Dim r   As Range
    
    Set sSelect = Selection.SpecialCells(xlCellTypeConstants)
    
    For Each sRange In sSelect.Areas
        For Each r In sRange.Rows
            Select Case Cells(r.Row, 3)
            Case "Sales"
                Cells(r.Row, 3) = "Buys"
            Case Else
                Cells(r.Row, 3) = "Internal"
            End Select
        Next
    Next