Compare column A with column D and retain only A values found

[jindon]

I don't understand how you want to apply this in your initial question.

UDF
Use in cell like
=RemoveDup(F3,"\")

In a Standard module

Function RemoveDup(ByVal txt As String, ByVal delim As String) As String
    Dim e
    With CreateObject("Scripting.Dictionary")
        .CompareMode = 1
        For Each e In Split(txt, delim)
            .Item(e) = Empty
        Next
        RemoveDup = Join(.keys, delim)
    End With
End Function

 

[vletm]

@Niranjan1979
It's can be D4 or E3 ... depends
but Your range(D12:I12) ... was tricky,
so I used 'UsedRange'.