The BSE benchmark Sensex down by 32 points to 18,761 in afternoon trade. Earlier Sensex rose marginally by 10 points in the opening trade in on selective buying by funds and retailers.The 30-share barometer, which had gained 111.13 points in the previous session, rose by 10.41 points, or 0.05 per cent, to 18,804.Similarly, the wide-based National Stock Exchange index Nifty fell by 12 points to 5,705.