I'd use something like:
Code:
Sub Demo()
Dim strAbbr, i As Long
strAbbr = ".Mr.Mrs.etc."
With Selection
If .Start > .Sentences.First.Start Then .MoveStart wdSentence, -1
If .End < .Sentences.First.End Then .MoveEnd wdSentence, 1
While InStr(strAbbr, "." & Trim(.Words.Last.Previous.Words.First) & ".") > 0
.MoveEnd wdSentence, 1
Wend
End With
End Sub