Selection.Expand (Word)

Expands the specified range or selection. Returns the number of characters added to the range or selection.

Expand (Unit)

Unit: A WdUnits constant that represents the unit by which to expand the range. The default value is wdWord.

With Selection 
 .Characters(1).Case = wdTitleSentence 
 .Expand Unit:=wdSentence 
End With