ADD HOURS

I HAVE A COLUMN WITH TIME DATA. I WANT TO CREATE ANOTER COLUMN THAT ADDS EITHER 1,2 OR 3 DEPENDING IF THE TIME IS WEST,MOUNTAIN OR CENTRAL (I WANT THIS TO BECOME E.S.T) NO MATTER WHAT I TRY IT DOES NOT ADD IT AND I DO NOT GET AN ERROR MESSAGE. THANKS FOR YOUR HELP. IE: REGARDING THE FIRE TRUCK I LIVE IN NYC NOT FAR FROM WTC AND I HAVE GIVEN ALREADY FOR BOTH POLICE AND FIRE DEPT ADDITIONNALY I HAVE BROUGHT FOOD, FLASHLIGHTS ETC.THAT IS A GOOD THING THAT YOU ARE DOING. THANKS AGAIN