In a large mixing bowl, combine dry cake mix and oats. Stir in melted butter and mix until crumbly.
Press half of mixture into the bottom of a greased 9 x 13 baking dish. In a small bowl, whisk together raspberry jam and water. Spread evenly over bottom layer of oatmeal mixture.
Crumble remaining oatmeal mixture of the top, pressing down firmly over the top. Bake at 375 for 20 minutes.
When cool, stir together in a small bowl powdered sugar and milk, one tablespoon at a time, until you get a drizzle consistency. Drizzle icing evenly over bars. Allow icing to cool before slicing into bars.
Serve immediately or wrap with plastic wrap in individual bars.