This really isn't a job for Find/Replace; rather, it calls for a macro like:
Code:
Sub Demo()
Application.ScreenUpdating = False
Dim strTxt As String, i As Long, j As Long
With Selection
For i = 1 To .Words.Count
For j = .Words.Count To i + 1 Step -1
If .Words(i) = .Words(j) Then
.Words(j).Delete
End If
Next
Next
End With
Application.ScreenUpdating = True
End Sub
For PC macro installation & usage instructions, see:
http://www.gmayor.com/installing_macro.htm