Maybe this code could solve your problem

if update (val1) or update(val2)

begin

insert into ch_track (id,action,field_name, datetime_1,user_name,old_val, new_val)

select ch.id,'u',@columns_updated,getdate(),'lcc001' from ch_track ch

inner join inserted i on ch.id=i.id

update ch_track

set old_val = d.old_val

from ch_track ch

inner join deleted d on ch.id=d.id

end