1. In a large bowl, beat margarine and cream cheese by hand until fluffy.
2. Add sugar and milk slowly until mixture is completely smooth.
3. In a food processor, add half the can of macaroons and process until the macaroons become crumbs.
4. Repeat step three for second half of can.
5. Place a thick layer of red velvet crumbs inside a trifle bowl. Top with a layer of frosting. Repeat this process until number of desired layers is reached or bowl is full. End with frosting layer, and top with red velvet crumbs.