[BP] Alternative to Thread

I’m scripting a game on UE4.8 with blueprints (yeah really…)
In my game, when the player moves from a cell to another, 2 for loops runs in order to generate “tiles” which are making the landscape.
The problem is when the loops are running they totally freezes the game until the generation is done.
I know that Threading is not possible with blueprints.
So my question is : What can I do in order to prevent my game from freezes when I run the generation loops (like a thread)

Thanks a lot in advance