Generate 1D bar code based on user defined input
You have content of type A and it contains a field called B , B is your serial fieldneedrst of all your field B must get multiple values , this can be set through Field UI. If you are going to collect more than 10 values per each content you can select unlimited values , but this has some DB overhead , after that drupal itself will create the form with multiple value , if you have chosen a specific number for that field for example 3 values , there will be 3 widget to get values , else if it is unlimited you will have an ajax add element button .
If this is not what you want and you want to enter the number of barcodes at the beggining then you must alter the form using hook_form_alter (you must write a module) , inside that hook add a counter element to your form (it gets the repeatation s count) and then use ajax to add widget to your form .
Each widget must be added to your field in your form , so drupal will understand that all the data inserted in these widgets relates to your field.
If you want to do it by writing a module and need some code ,I can add some code later.