check message for wrong serial no in VLO1N

Hi Expert,

Our company is a tractor manufacturer .Production department does the Backlashing and provide the serial no. after that when sales department is doing sale. Firstly Create sales order(VA01) and after that do the PGI(vl01n) and at the time of PGI when user give the serial no to that particular tractor. IF user gives the wrong Serial no to the system then system is not flashing any error and accepting the wrong serial no.

Expert please gives me the solution for wrong serial no. how can be give the check for the wrong serial no.

Thanks and regards

Sarvottam Tomar