hi Ben Lewis
or with the more adaptable dictionary
Option Explicit
Sub ptesttwo()
    Dim y$, x, z
    With CreateObject("Scripting.Dictionary")
        .CompareMode = vbTextCompare
        For Each z In Split(Range("A3"), ",")
            y = Trim(z)
            If Not .exists(y) Then
                .Add y, y
                x = x & IIf(x <> "", ",", "") & y
            End If
        Next
        Range("A3").ClearContents
        Range("A3") = x
    End With
End Sub