How to wait random seconds to go to the next page using either webservice or JavaScript

Hello,
I'm building a survey using quota. To prevent overbooking on quota I created a branch in the surveyflow where I check if an option in the survey is selected AND if the quota has been met. If so then display the same block again. Using displaylogic on multiple choice options prevents the display of an option where the quota has been met.
Only we have a lot of respondents starting at about the same time. Because the new number of selections on an option in a quota is set to slow overbooking is possible. How can I slow down the process checking the quota so the number in the quotasettins can be updated first before the process goes on?
Or is it possible to use a webservice to update the quota after a respondent finishes the first time selection?