Duck Genetic questions

I know how blue works. If you cross blue with blue you get 50% blue, 25% black, and 25% splash. My question is a bit more complicated.

I wanted to bring some Blue looking ducks into my flock. My friend has some Blue Swedish that his kids are bringing to the fair. I was going to mate his Blue Swedish with my Black Swedish/Rouen cross. My Black Swedish/Rouen are black with a spotted bib. The crosses crossed with each other made an all black duckling. How many eggs would I need to get to make sure the combo gets a blue. My Swedish/Rouen is the female and my friend's Blue Swedish would be the male.