I used to use

code = code + 1
but when the table was indexed I had problems

Then, a guy from this forum gave me the code below

******************************************
dimension lctemp[1]
select max(client.CODE) from client ;
into array lctemp
lctemp[1] = IIF(_tally=0,1,lctemp[1] + 1)

APPEND blank
replace client.code with lctemp [1]
**************************************

It works well, however if it's the first record it
gets of an empty table it generates a null value to the code