the user permission problems........need your help.....tkx......

i have a group "customer",plan to the member of customer
can only add,edit and delete the ablum,item of themself.
but,if i activate the [core]add sub-ablum,[core]add sub-item,[core]edit item, [core]Delete item,
the member of customer have the add and edit of permissions,themself can edit and delete the other's item or ablum.
so, who can tell me what can i do that the membere of group can only work for themself,not edit or delete the others.
tkx.....