Sub Demo()
Application.ScreenUpdating = False
Dim Tbl As Table, Cll As Cell
For Each Tbl In ActiveDocument.Tables
  For Each Cll In Tbl.Range.Cells
    With Cll.Range
      If Len(.Text) > 2 Then
        Do While .Characters.First.Text = " "
          .Characters.First.Text = vbNullString
        Loop
      End If
      If Len(.Text) > 2 Then
        Do While .Characters.Last.Previous.Text = " "
          .Characters.Last.Previous.Text = vbNullString
        Loop
      End If
    End With
  Next
Next
Application.ScreenUpdating = True
End Sub