Hola Enrique como estas?
creo que este es el codigo que necesitas.
******************ATRAS************************
IF BOF()
GO TOP
THISFORM.command1.ENABLED=.F.
THISFORM.command2.ENABLED=.F.
ELSE
SKIP -1
THISFORM.command3.ENABLED=.T.
THISFORM.command4.ENABLED=.T.
IF BOF()
GO TOP
THISFORM.command1.ENABLED=.F.
THISFORM.command2.ENABLED=.F.
ENDIF
ENDIF
THISFORM.REFRESH
******************ADELANTE************************
IF EOF()
GO BOTTOM
THISFORM.command1.ENABLED=.T.
THISFORM.command2.ENABLED=.T.
ELSE
SKIP
IF EOF()
GO BOTTOM
THISFORM.command3.ENABLED=.F.
THISFORM.command4.ENABLED=.F.
ENDIF
THISFORM.command1.ENABLED=.T.
THISFORM.command2.ENABLED=.T.
ENDIF
THISFORM.REFRESH
******************FIN****************