Preheat oven to 350 degrees F (175 degrees C). Grease one 9x13 inch baking pan.
In a large bowl cream together the brown sugar, margarine, and raisin paste. Sift together the flour, rolled oats, and baking soda; stir into the creamed mixture. The mixture should be crumbly. In a smaller bowl, mix together the rest of the raisin paste, the chopped raisins, raisin juice concentrate, water, and sugar.
Pat down 1/2 of the crumbly oat mixture into the prepared baking pan. Spread the raisin filling evenly onto the oat crust. Top with the remaining oat mixture, and bake in the preheated oven for 45 minutes, until the top crust begins to brown. Let cool and cut into squares.