Number sequence based on enum value on the form

Hi Experts,

I have a requirement that I need to to generate different number sequence for a field based on the selection of  an enum element in the form. example if the user selects enum A the number sequence should be A1,A2,etc. if its B it should be B1,B2, etc. From other posts I understand that it is possible in AX, Is there any step by step reference / sample for the same ? 

Thanks in advance