HEAT oven to 350°F. Mix pretzels, 1/4 cup sugar and margarine; press onto bottom of 13x9-inch pan. Bake 10 min. Cool.
BEAT cream cheese, remaining sugar and milk until blended. Stir in Cool Whip; spread over crust. Refrigerate.
ADD boiling water to jelly powder in large bowl; stir 2 min. until completely dissolved. Stir in cold water. Refrigerate 1-1/2 hours or until thickened (spoon drawn through leaves definite impression). Stir in strawberries; spoon over cream cheese layer. Refrigerate 3 hours or until firm.