Start with the crust: Mix the pecans and flour together. Melt butter; add to mixture and stir until moist.
Press into a deep ungreased 9x11 inch pan--crust should be thin.
Bake until lightly brown; cool completely.
Blend the cream cheese and Cool Whip together until smooth. Add sugar slowly until mixed well (make sure the Cool Whip is defrosted and the cream cheese is at room temperature before starting). Spoon filling into crust and let sit in the refrigerator while you mix the pudding.
Mix the 2 boxes of pudding with the milk. When the pudding is thickened, add it to the top of the cream cheese mixture. Let set in the refrigerator.
Next spread the last tub of Cool Whip on top of the pudding, being careful not to mix with the pudding.