how to validate a random variable in jmeter, if it is unique or not for requests

Here I want to generate a random 9 digit number, I have achieved it using a config element->Random Variable. Now I need to check if that number is unique or not, so for that, I have used If the controller and passed a condition checking the previous response message is true or false, if the output is false, then it will again generate a Random variable and this time a newly generated will be passed onto it.

But till how many times I will check this using If controller, so needs an alternative solution for the same. Below is the hierarchy of my test plan: Random variable Sampler HTTP Request(Here random variable is passed) If Controller(Condition: ${JMeterThread.last_sample_ok}==false) Random Variable generated again Sampler HTTP Request(Here random variable is passed)