Glass Block Jello

I saw this on a recipe site called Our Best Bites and thought it looks awesome. Here's the website if you wanna take a look: www.ourbestbites.com

Ingredients:
4+ (3oz) packages of assorted jello flavors (diff colors)
2 packets unflavored gelatin (Knox original gelatine)
1 14oz can sweetened and condensed milk (could possibly sub white grape or pear juice if not keen on SC milk)

SPRAY 4+ small food storage containers
COMBINE 1 C boiling water w/1 pkg of jello (no cold water added)
REFRIGERATE atleast 4 hours

AFTER jello has set, bring 1 1/2 C of water to boil. In mean time, sprinkle 2 packets of inflavored gelatine over 1/2 C cold water and allow to stand about 4 minutes.
POUR boiling water over dissolved gelatine
ADD sweetened and condensed milk, mix well and allow to cool to room temp.

LIGHTLY spray 9x13 pan.
CUT colored jello and gently toss into pan.
POUR cooled milk mixture over colored jello.
PUSH down gently any blocks that are floating too far out of mixture.
PLACE in fridge over night.
CUT into sqaures or use cookie cutters after set.