trim not trimming in vb.net

I have this loop which creates the string but leaves a space at the end.
The Chr(32) is putting the space in between the words.
How can I get it not to leave a space at the end.

  For Each drRecordW As DataRow In dtCodeWords.Rows
                    StrShortString = StrShortString & drRecordW("word") & Chr(32)
                    RTrim(StrShortString)
                    Debug.Print(StrShortString)
                Next

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