Autoincrement Alphanumeric number using PeopleCode

Below function was created to autoincrement aplhanumeric field, 

3 parameters are needed for executing the function, Previous or max string value, numbers of characters in a field, number of integer values in a field.

Function auto_incr(&Var As string, &Nc As integer, &ni As integer) Returns string

   Local integer &max_int, &i_str;

   Local boolean &maxint;

   Local boolean &max_str;

   Local string &str_i, &str_e, &substr;

   

   &str_i = "";

   For &c = 1 To &ni

      &str_i = &str_i | "9";

   End-For;

   &max_int = Value(&str_i);

   &str_e = Substring(&Var, &Nc + 1, &ni);

   &i_str = Value(&str_e);

   

   If &i_str < &max_int Then

      &i_str = &i_str + 1;

      &var1 = Substring(&Var, 1, &Nc) | &i_str;

   Else

      &maxint = True;

      &str_i = "";

      For &c = 1 To &ni - 1

         &str_i = &str_i | "0";

      End-For;

      &str_i = &str_i | "1";

   End-If;

   

   If &maxint = True Then

      For &c = &Nc To 1 Step - 1

         &substr = Substring(&Var, &c, 1);

         rem check between 65 to 90;

         If Code(&substr) >= 65 And

               Code(&substr) < 90 Then

            &substr = Char(Code(&substr) + 1);

            &var1 = Replace(&Var, &c, 1, &substr);

            &var1 = Replace(&var1, &Nc + 1, &ni, &str_i);

            Break;

         End-If;

      End-For;

   End-If;

   Return &var1;

End-Function;

&str = "AZZ899";

&res = auto_incr(&str, 3, 3);

WinMessage(&res);