Sub DeleteCap3Word()
Dim oRng As Word.Range
Set oRng = ActiveDocument.Range
  With oRng.Find
    .ClearFormatting
    .Text = " [A-Z]{3} "
    .Replacement.Text = " "
    .Forward = True
    .Wrap = wdFindStop
    .Format = True
    .MatchCase = True
    .MatchWholeWord = True
    .MatchWildcards = True
    .MatchSoundsLike = False
    .MatchAllWordForms = False
    While .Execute
      Select Case Trim(oRng)
       Case "USB", "PSA"
       
       Case Else
         oRng.Text = " "
     End Select
     oRng.Collapse wdCollapseEnd
   Wend
  End With
End Sub