Concatenate Based on the Criteria

I'd go with any one of the Concatenation UDF's floating on the web.

However, you should note that the parameters repeat themselves in D:D which will concatenate quite a number of cells.

Function ConcatIf(ByVal compareRange As Range, ByVal xCriteria As Variant, Optional ByVal stringsRange As Range, _
                    Optional Delimiter As String, Optional NoDuplicates As Boolean) As String
                    
    Rem the first three argumens of ConcatIf mirror those of SUMIF
    Rem the Delimiter and NoDuplicates arguments are optional (default "" and False)
    Dim i As Long, j As Long
    
    With compareRange.Parent
        Set compareRange = Application.Intersect(compareRange, Range(.UsedRange, .Range("a1")))
    End With
    
    If compareRange Is Nothing Then Exit Function
    If stringsRange Is Nothing Then Set stringsRange = compareRange
    Set stringsRange = compareRange.Offset(stringsRange.Row - compareRange.Row, _
                                            stringsRange.Column - compareRange.Column)
    
    For i = 1 To compareRange.Rows.Count
        For j = 1 To compareRange.Columns.Count
            If (Application.CountIf(compareRange.Cells(i, j), xCriteria) = 1) Then
                If InStr(ConcatIf, Delimiter & CStr(stringsRange.Cells(i, j))) <> 0 Imp Not (NoDuplicates) Then
                    ConcatIf = ConcatIf & Delimiter & CStr(stringsRange.Cells(i, j))
                End If
            End If
        Next j
    Next i
    ConcatIf = Mid(ConcatIf, Len(Delimiter) + 1)
End Function