Let a single keystroke take you one sentence forward, or one sentence back, using Word's definition of a sentence. We assign these macros to Ctrl+Alt+Right and Ctrl+Alt+Left, respectively.

Sub NextSentence()
'    NextSentence Macro created 8/2/2000 by Peter N Roth
    Selection.MoveRight Unit:=wdSentence
End Sub

Sub PrevSentence()
'    PrevSentence Macro created 8/2/2000 by Peter N Roth
    Selection.MoveLeft Unit:=wdSentence
End Sub