Tell us what you are trying to do? I would like for a member to type a number (in a certain range) and the system to check whether that number is available. For example, the member is interested in purchasing number 1234 by entering this value in the cred form, the system needs to confirm availability.
Is there any documentation that you are following?
This way if the user will try to create a number post with the title that is already taken, the validation message will show, asking to enter a different number.