"vba array formula to concatenate"

I have data in col a and col b
I want concatenate all data in col a by criteria in col b, criteria in col b = "union"
Example b2,b5,b10 = union
Then result in d3 = (a2,b5,b10).value
I have formula array vba
D3 = application. Transpose(join([b:b="union",a:a,""],",")
How i cant do use formula array like it use join

Yes i know but i has see by jindon post
Its can do

http://www.excelforum.com/excel-prog...-new-post.html
In this post only range in this cell not offset cell by criteria

Sub test()
    [d3] = Join(Filter([transpose(if(b1:b1000="union",a1:a1000))], False, 0))
End Sub

thankyou jindon how if add criteria

Sub test()
    [d3] = Join(Filter([transpose(if(b1:b1000="union",a1:a1000))], False, 0))
' and test to do function but error 
 Function test(cr As String, rng As Range) As String
      test = Join(Filter([transpose(if(rng=cr,rng.offset(,-1)))], False, 0), ",")
  End Function

End Sub

Sub test()
    [d3] = VJoin(Range("a1:b1000"), 2, "union", 1)
End Sub

Function VJoin(rng As Range, CriteriaCol As Long, myStr, joinCol As Long) As String
    If Not IsNumeric(myStr) Then myStr = Chr(34) & myStr & Chr(34)
    With rng.Parent
        VJoin = Join(Filter(.Evaluate("transpose(if(" & rng.Columns(CriteriaCol).Address & "=" & _
                myStr & "," & rng.Columns(joinCol).Address & "))"), False, 0))
    End With
End Function

Sorri jindon i dont see its has solved thankyou