Generating unique client numbers based on field option choices
I need to generate a number based on the result of a field's options, and this number needs to be unique, increasing, and dependent on the outcome of a field option. For example, the field Nature of Exam has 5 options. If I choose option 1, my choice auto populates a customer number field with P11/0001 for the first instance, P11/0002 for the second instance, and so on. If my choice is option 2 or 3 or 4 or 5, that same field is then populated with H11/0001, etc. The two counts are independent of each other. I am racking my brains trying to figure out how to do this as I am not very familiar with functions. Any help would be appreciated.