am not able to use for each row in trigger

this is my code

create trigger trig_delete_tblworkdocketchild
on tblworkdocketchild
for each row delete
as
update tblmaterialin set tblmaterialin.quantity= deleted.rused +tblmaterialin.quantity
from tblmaterialin,deleted
where tblmaterialin.material = deleted.rpaper

i dnt know wi i get error...
helep me to fix this error