SSRS distinct lookupset function

I'm using Join(Lookupset) to find unique group values which returns a sequence number. This is my function:

Join(LookupSet(Fields!itemId.Value & Fields!UseByDate.Value & Fields!rackId.Value
    , Fields!itemId.Value & Fields!UseByDate.Value & Fields!rackId.Value
    , Fields!CustomerSeqNo.Value
    , "PickingList"), ",")

The problem is on some items there are multiple transactions. I want to remove the duplicates.

I found a blog http://blogs.msdn.com/b/bobmeyers/archive/2012/06/18/creating-short-lists-using-the-lookupset-function.aspx but could not get SSRS Report Builder to reference Linq assembly. My issue is

How can I just show the unique values?

You don't need Linq, but you do still need custom code (in BIDS go to Report -> Report Properties -> Code)

You can put a RemoveDuplicates function in here, something like this:

Public Shared Function RemoveDuplicates(m_Array As Object()) As String()

    System.Array.Sort(m_Array)
    Dim k As Integer = 0
    For i As Integer = 0 To m_Array.Length - 1
        If i > 0 AndAlso m_Array(i).Equals(m_Array(i - 1)) Then
            Continue For
        End If
        m_Array(k) = m_Array(i)
        k += 1
    Next

    Dim unique As [String]() = New [String](k - 1) {}

    System.Array.Copy(m_Array, 0, unique, 0, k)

    Return unique

End Function

To use it in your Join:

Join(Code.RemoveDuplicates(LookupSet(...)),",")