Hi Mary Annie. I hope when you say "silk" you are talking about the texture. Many silk pies were previously made using raw eggs which we are now advised to avoid using. The sweetened condensed milk and the whipped topping should give you a similar texture.

Here is a recipe that I hope will suit your needs.

No-Bake Key Lime Pie:

1 4oz. can sweetened condensed milk
3/4 c. lime juice
Grated rind of 1 lime
1-2 drops green food coloring (optional!)
1 8oz. container of whipped topping
1 graham-cracker crust (9-10 inches)
Lime Slices
Whipped cream or whipped topping

Mix condensed milk and lime juice. Next add grated rind and food
coloring. Fold in whipped topping. Pour into crust and chill
overnight. Top with whipped cream and lime slices. Serves 8