Drain apricots and pineapple, reserving the juice. Set juice in freezer to chill while you do the next steps.
Chop apricots in bite size pieces.
Dissolve jello in boiling water in a large bowl.
Add 1 cup of the cold fruit juice, reserve remaining juice.
Chill until slightly jelled (about 30 minutes).
Add fruit and marshmallows to slightly jelled jello.
Pour into 9x13 pan.
Chill until firm.
In a small sauce pan, combine sugar, flour, egg and 1 cup of saved juice.
Cook over low heat till thick.
Remove from heat and add butter.
Cool in fridge.
Fold in Cool Whip.
Spread topping on top of jello.