store proc's and triggers

hello all, i have a stored procedure that is to do some specific work once the routine hits the exception section. When the stored procedure is manually called by running execute procedure, the exception is caught and the work is done however, when the trigger on the tables fires off automatically by the system, the exception section is skiped over and the specified work is not done. Has anyone run into this before? Is there (and should there be) a difference between the two methods? thanks again! Tom