Does this cutting have roots? If so, the flowers will continue to form. If not, they will continue to form if there is sufficient light, even without roots!
Once you are ready to harvest the pollen, there are different techniques.
I was reading a thread where someone cuts the flowers just before they spill, very carefully and thoroughly dries them, vacuum packs with desiccant, and stores in a cool dark place, for years.
A quick run on how I learned @Muleskinner’s trick for storing pollen is is here.