I will try to answer by example:

func CustUpdTrig && Customer table update trigger
local lcNewName
lcNewName= customer.Name
...
Write2Log( 'Customer', oldval('Name'), lcNewName, datetime() )
...

func Write2Log
para cTablName, cOldVal, cNewVal, dTimeStmp
...
insert into LogTabl ( table, old, new, ts) ;
value ( cTablName, cOldVal, cNewVal, dTimeStmp)
...

Put those two functions in your database stored procedure