Can you use white almond bark instead of white chocolate?

No, but you can use almond bark to make an imitation marzipan with the following recipe:

8 oz. almond bark

1 1/2 cups confectioner's sugar

4 TB corn syrup

1-2 tsp almond extract

1. Melt almond bark in saucepan over medium heat.

2. Remove from heat and let cool, but don't let it get so cool that it solidifies again.

3. Mix in almond extract.

4. Using mixer, gradually beat in confectioner's sugar. Mixture will be crumbly.

5. Mix in corn syrup. Mixture will still be somewhat crumbly.

6. Turn out onto generously floured surface, and knead, working in small amounts of flour, until it reaches a dough-like consistency.