David Weinberg will call his mother in Toronto on Sunday morning, as usual, to wish her a happy Motherís Day. Sunday afternoon heíll make another call ó for an end to the genocide in Sudan ó as the leader of a rally in Central Park.Weinberg, 23, a senior at Yeshiva University, is the founding director of Not Now Not Ever, a nonprofit organization he and two Stern College students launched a few months ago to protest the ongoing Sudan tragedy. The group already has gone national.The Not Now Not Ever rally will begin at 4:30 p.m. at a clearing in the park near 72nd Street and West End Avenue. About 3,000 people, many of them fellow college students from several states, are expected at the event, Weinberg said.Speaking to those who usually spend Motherís Day with their families, he said, ìWe want to say Ö there are thousands of people being ravaged thousands of miles away.îSudan has been the site of mass killings and forced slavery at the hands of the African countryís Islamic government since a civil war with Christians and animists in the south began two decades ago. Estimates of the number of Sudanese killed is in the high six figures, and millions have become refugees.Weinberg, with Cindy Bernstein and Rebecca Stone from Stern, became interested in the topic as students this term in a videoconference class on ìNational Sovereignty and Human Rights.îìItís about genocide,î said Weinberg, whose family lost relatives in Poland during the Holocaust. ìWe have to make people understand that ëNever again!í is more than an empty slogan. We want to create public awareness. Public awareness will create political pressure. We can make a difference.îHe and the Stern students contacted friends and human right activists at campuses across the country.The Anti-Defamation League and American Jewish World Service, whose president, Ruth Messinger, will speak at Sundayís rally, have supported the studentsí ìvery grassroots thing. YU has been remarkably helpful,î Weinberg said.Not Now Not Ever plans to hold a national rally ìon a much bigger scaleî in Washington this summer, he said.On Sunday, Weinberg said he will introduce the speakers and coordinate the event. Afterward, heíll call his mother again.For information about the rally, call Not Now Not Ever at (646) 302-4761; e-mail, firstname.lastname@example.org.