Bring the cherry juice with preserving sugar to the boil (according to the instructions of the preserving sugar manufacturer) and add the amaretto when boiling. Don`t be fooled that 150 ml is a lot. Most of it dissipates when you cook it anyway. If you want it with a slight alcohol note, add a dash of amaretto after boiling.
I came to the recipe after I made the Amarena cherries and had the cherry juice left over from the cherries and then boiled it up to make a jelly.