Option Explicit

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
    ' code base by Mike Rickson, MrExcel MVP
    ' used as exactly like SUMIF() with two additional parameters
    ' of delimiter and "no duplicates" as TRUE/FALSE if concatenated values
    ' might include duplicates  ex. =ConcatIf($A$1:$A$10, C1, $B$1:$B$10, ",", True)

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