Prepare pie crust according to package directions. Put blueberries into saucepan, add sugar, one-half cup water and lemon juice and cook over a slow heat. Dissolve cornstarch in remaining one-fourth cup cold water. As soon as blueberry mixture comes to a boil stir in cornstarch and remove from fire. Let cool.
Roll out two-thirds of the pie crust large enough to line the bottom and sides of an eight- inch pie plate. Pour in filling. Roll out remaining crust and cover top of pie. Seal edges with a little milk, crimp. Perforate with fork or cut air holes in center of crust.
Bake at 450 f or 232 C for ten minutes. Lower heat to 350 degrees and bake 20 minutes or until crust is lightly browned.