For example:
Sub Demo()
Application.ScreenUpdating = True
Dim Rng As Range
For Each Rng In ActiveDocument.StoryRanges
With Rng
With .Find
.ClearFormatting
.Replacement.ClearFormatting
.Forward = True
.Wrap = wdFindStop
.MatchWildcards = True
.Text = "[! ^13^l^m^n^s^t]{2,}"
End With
Do While .Find.Execute
.End = .End - 1
.HighlightColorIndex = wdTurquoise
.Collapse wdCollapseEnd
Loop
End With
Next Rng
Application.ScreenUpdating = True
End Sub
The above code finds and highlights any string of more than two characters, excluding white-space characters (spaces, tabs, paragraph breaks, etc.) not followed by a white-space character.