turning off a trigger

I'm relatively new to Informix and am unsure how to proceed. I'd like to create a trigger that upon update of a record in a table, will change the same field in one or more records of the same table by the same amount. So if the value in the field is increased by 10 for example, that field in another record (or records) is also increased by 10. (A second table is used to determine which additional records are changed). But... I don't want the second change(s) to invoke the trigger, only the original change. I think I somehow need to disable the trigger while the subsequent change(s) is/are made. TIA, Rob