Heat 1/4 cup sugar, lemon juice, & 1/4 cup water in a saucepan over medium-high heat, stirring, until the sugar dissolves. Remove from the heat, and stir in the vanilla extract. Let cool. Beat the remaining 1 cup sugar & the cream cheese with a mixer on medium speed until smooth & light. Add the heavy cream & beat on high speed until smooth & the consistency of whipped cream.

Cut the cake into 1 inch slices & brush each side with the lemon syrup. Cut into cubes. Arrange half of the cake cubes in the bottom of a 13 cup trifle dish, or large clear bowl. Sprinkle evenly with a layer of blueberries. Dollop half of the cream mixture over the blueberries & gently spread. Top with a layer of strawberries. Layer the remaining cake cubes on top of the strawberries, & top with the other half of the cream. Arrange the remaining blueberries & strawberries on top.

Cover & refrigerate 1 hour.