Heat oven to 350°F. Spray bottom of 13×9-inch pan with cooking spray.
In large bowl, stir cookie mix and 1/2 cup softened butter until mixture forms coarse crumbs. Spread mixture evenly in pan; press lightly.
In large bowl, beat cream cheese, 3 1/2 cups powdered sugar, eggs and vanilla with electric mixer on low speed until blended; scrape bottom and side of bowl. Beat on high speed until smooth. Beat in 1/3 cup melted butter until blended. Pour over cookie mixture; spread evenly.
Bake 30 to 35 minutes or until golden brown. Cool completely, about 2 hours.
Just before serving, in medium bowl, mix strawberries, 2 tablespoons powdered sugar and the lemon juice. Let stand 10 minutes, stirring occasionally. To serve, cut bars into 5 rows by 3 rows. Top each with strawberries and a dollop of whipped cream. Cover and refrigerate any remaining bars.