Giving up all its initial gains, the Sensex at the Bombay Stock Exchange stood 76 points, or 0.4 percent in negative territory, at 18,441 in afternoon deals, amid volatile trade, a short while ago. Earlier in the morning, however, the Sensex had opened with a gain of 32 points, or 0.2 per cent, at 18,550, on mild buying by investors, amid firm regional bourses. The 30-share Sensex had advanced over 188 points in the previous two trading sessions.Key stock indices in China, Hong Kong, Singapore, Taiwan and South Korea had moved up by between 0.1 percent and 2.7 percent, today. The rupee declined for fourth day in a row by losing 15 paise to Rs 55.36 per dollar in early trade today following sustained dollar demand from importers.However, a higher opening in the equity markets and slightly weak dollar against the euro overseas amid continued foreign fund inflows limited the fall