A VITAMIN STORE IN SALINAS WAS ROBBED THIS AFTERNOON (TUES).       OFFICIALS SAY A MAN ENTERED THE BUSINESS AND DEMANDED MONEY FROM THE CLERK, THREATENING HE HAD A GUN IN HIS WAISTBAND.      THE SUSPECT TOOK OFF WITH AN UNDETERMINED AMOUNT OF MONEY.     THE ROBBER HAS BEEN DESCRIBED AS A WHITE MALE IN HIS FORTIES.     HE WAS LAST SEEN RUNNING SOUTHBOUND ON NORTH MAIN STREET, WEARING A GRAY BEANIE, DARK BLUE PANTS, AND A WHITE        T-SHIRT OVER A GRAY LONG-SLEEVED SHIRT.