I'm not sure which change detection VI you are referring to, but if it has output terminals, then if you place this in a while loop, then the loop can not iterate until this VI has finished. Just check the output, set up a logic structure to check and see if it has "ticked" and then choose whether to continue or not. It would basicaly be two nested loops. If you get a chance, post information about the change detection VI and we may be able to help you further.
J.R. Allen