1. Read your client details into variables, say cname="Uday", clocaiton="India" etc....
2. Look in DB for already a record exists with the above details. Write DBFunction like checkCustomer(ip1,ip2 etc) which returns say count=0 then 2A. write script to insert customer in your application.
2B. If count is more than 1, then customer details already exists.
There is direct function in QTP that valides your case, you have to handle your own way.
I'm thinking that it is technically possible to do this type of checking. It's more a matter of how important for the situation to exist. In a bank, I would not want to be listed as two different people with the same ssn. In gmail contacts it is OK that I have multiple contacts with the same first and list name.
I think he might be generating random data to insert and doesn't want to insert it if it has already been used. If that is the case, the approach Uday suggested would be good. Write a query using the variables you intend to insert and if it produces any results, it has already been used.